Technical Specifications

LBMA considers that the appearance of Bars is important, firstly because of the technical reasons described below and secondly because the maintenance of high standards of surface finish indicates a good level of quality control in general. A poor Bar appearance might, on the other hand, suggest that standards of refining or assaying are less than desired.

The decision on whether a Bar meets the physical standards of the London bullion market is the responsibility of each Vault’s manager, who has complete discretion in relation to which Bars should be accepted. LBMA facilitates a consistent approach to such decision-making by arranging regular meetings of the Vault managers and by providing guidance to allow them to distinguish between, on the one hand, minor imperfections, and on the other, serious defects which require the Bar to be rejected.

2.1 General Description of Good Delivery Bars

2.1.1 Weighing

R Bars must be weighed as provided for in Annex B, and in accordance with the procedure set out in Annex C.

2.1.2 Casting Method

R Bars must be produced in graphite or cast iron moulds, either by the:

• conventional method of pouring molten metal into them; or
• non-conventional method of melting grain in an induction tunnel system, or in the case of silver, by continuous casting.

Bars cast in open moulds should be produced at a single pouring.

G Any Refiners wishing to convert to the use of the above-mentioned non-conventional methods of Bar production must submit a proposal to LBMA for consideration prior to implementation. Tunnel furnace production is known to have a risk of density/porosity, and must be minimised. LBMA may then request that two Bars cast using the proposed alternative method must be sent to London for visual inspection. Once the Bar inspection is complete, the Bars may then be sent to the Referees for further analysis to ensure that the Bars meet the specifications in these Rules. The Refiner must pay for LBMA’s costs in the examination and testing of the Bars.

2.1.3 Shape

R Bars must be ingot-shaped (i.e., having a trapezoidal cross-section, both along the length and across the width of the Bar) with sufficient undercut to facilitate handling but without resulting in the width of the bottom surface being so narrow that the Bar cannot be safely stacked.

G Bars must be easy and safe to handle. Refiners must ensure that their Bars will stack safely when considering the dimensions of their proposed Bars. Proper stacking and handling of a Bar will be taken into consideration during Bar inspections. It is important that the edges of the Bars must not be sharp, so to avoid the risk of injury during handling.

2.1.4 Appearance

R Refiners must make sure the following faults, especially on top surface of a Bar, are avoided:

• Irregularities such as surface cavities, cracks, holes or blisters (debris and water can accumulate in such irregularities which can affect the weight of the Bar and accumulated water can cause an explosion when the Bars are melted);
• Excessive shrinkage (i.e. the concavity of the top face of the Bar and any concentric cooling rings) must not significantly affect the clarity of the Bar marks or the safe stacking of the Bars;
• The sides and bottom (smaller) surface should be flat and reasonably smooth (which does not imply the need for a mirror-like finish) and free from cavities and lumps;
• Excessive layering, if it can result in dust or dirt being trapped and thus affecting the recorded weight of a Bar.
• Excessive post-production polishing, if it makes the Bar too smooth thus impacting the safe stacking of the Bars.

G Bars must be of good appearance. In the case of new production of gold Bars, hammering is not acceptable, nor are any attempts to conceal defects, for example by burnishing. In some cases, the use of a ball pein hammer to flatten a sharp protrusion may be considered acceptable. In the case of silver Bars, it is recognised that a small degree of hammering or other surface treatment is sometimes required but such hammering should not affect the markings or shape of the Bar.

2.1.5 Marks

R All marks should include:

• stamp of the Refiner (which, if necessary for clear identification, should include its location);
• assay mark;
• fineness (Refiners must apply a consistent font to all digits);
• serial number (which must not comprise of more than 11 digits or characters);
• year and month of manufacture unless incorporated as the first digits in the Bar number.

All marks should be clear and the height of characters used for the fineness, the date and the serial number should be a minimum of 12 mm.

Gold Bars must be marked on the larger of the two main surfaces (the cast surface at the top of the mould) using conventional (pressure) stamping or dot matrix (pneumatic punching). If pneumatic punching is used, the marks must be no less clear and at least as durable as if conventional stamping had been used.

Silver Bars may alternatively be marked on the end of the Bar if marked using a dot matrix method so that the marks can be read from the top edge downwards (see Annex F).

G Any Refiners intending to change to dot matrix marking should notify the GDL Team and send a new drawing and photo in advance, together with the date from which the new marking method will be used. Failure to provide this material in advance may result in Bars being rejected on arrival at a Vault. For Refiners whose Bar dimensions are currently not compliant with LBMA’s recommended sizes, changing from pressure to dot-matrix marking will trigger a requirement for Bars to be brought within the recommended dimension range.

If Bar numbers are to be reused each year, it is strongly recommended that the year of production is shown as the first four digits of the Bar number although a separate four digit year stamp may be used in addition. If Bar numbers are not to be recycled each year, the year of production must be shown as a separate four-digit number.

Since January 2019, Refiners must include the month of production in either two-digit form or a code (LBMA must be notified) the Bar serial number or year stamp (for example, January 2019 = “0119”). Alternatively, submit the last Bar number used on the last day of each month to the GDL Team by email at gdl@lbma.org.uk.

Any existing Refiners that are submitting the last Bar number used on the last day of each month, must include the two-digit month stamp in their Bar Markings, by 31 March 2023.

2.1.6 Weight Stamps

R It is strongly recommended that weights should not be stamped on Bars, however if Bars are stamped in such a way, the unit of weight must be shown.

G By way of background, when Bars are weighed by an Approved Weigher, their weights, which may be different from those determined by the original Refiner, will prevail. In addition, any change in the weight of a Bar caused by future handling or sampling would result in a divergence between the weight-list weight and the marked weight.

2.1.7 Specifications for a Good Delivery Bar

All Refiners must comply with the following specifications for Gold and Silver.

Gold Bars

R Physical settlement of a loco London gold trade is a Bar conforming to the following specifications:

Weight:

• Minimum gold content: 350 fine troy ounces (approximately 10.9 kilograms).
• Maximum gold content: 430 fine troy ounces (approximately 13.4 kilograms).

The gross weight of a Bar should be expressed in troy ounces, in multiples of 0.025, rounded down to the nearest 0.025 of a troy ounce.

Dimensions:

The permitted dimensional ranges for a gold Bar are as follows:

• Length (Top): 250 mm +/- 40 mm Undercut: 5º to 25º.
• Width (Top): 70 mm +/- 15 mm Undercut: 5º to 25º.
  
  The undercut refers to the degree of slope on the side and ends of the Bar and is represented by the angle of deviation from the vertical of the side and end surfaces.
• Height: 35 mm +/- 10 mm.

Fineness: the minimum acceptable fineness is 995.0 parts per thousand fine gold.

Marks:

• Serial number (see additional comments in Section 2.1.5 above).
• Stamp of the Refiner.
• Fineness (to four significant figures*).
• For Bars produced from January 2019 onwards, the year and month of manufacture (see additional comments in Section 2.1.5 above).
  
  *Since January 2018, gold and silver Bars can be marked with up to five significant figures, if required by national standards. However, it must have a point or comma delimiter to avoid confusion and potential ambiguous additions. The weight list would only include four significant figures.

Silver Bars

R The physical settlement of a loco London silver trade is a Bar conforming to the following specifications:

Weight:

• Minimum gross weight: 750 troy ounces (approximately 23 kilograms).
• Maximum gross weight: 1100 troy ounces (approximately 34 kilograms).
  
  It is recommended that Refiners should aim to produce Bars within the following weight range:
• Minimum gross weight: 900 troy ounces (approximately 28 kilograms).
• Maximum gross weight: 1050 troy ounces (approximately 33 kilograms).
  
  Bars produced prior to 1 January 2008 having a weight in the former wider range of 500 to 1250 troy ounces will continue to be acceptable, though it is expected that these will be phased out when the number of such Bars in the Vaults has declined to nearly zero.
  
  The gross weight of a Bar should be expressed in troy ounces in multiples of 0.10, rounded down to the nearest 0.10 of a troy ounce.

Dimensions:

The permitted dimensional ranges for a silver Bar are as follows:

• Length (Top): 300 mm +/- 50 mm Undercut: 5º to 15º.
• Width (Top): 130mm +/- 20 mm Undercut: 5º to 15º.
• Height: 80 mm +/- 20 mm.

Fineness: the minimum acceptable fineness is 999.0 parts perthousand silver.

Marks:

• Serial number (see additional comments in Section 2.1.5 above).
• Stamp of the Refiner.
• Fineness, expressed to either three or four significant figures*.

• For Bars produced from January 2019 onwards, the year and month of manufacture (see additional comments in Section 2.1.5 above).
  

  * Since January 2018, Bars can be marked with up to five significant figures, if required by national standards. However, it must have a point or comma delimiter to avoid confusion and potential ambiguous additions. The weight list for these instances would only include four significant figures.