Weighing: Bars should be weighed in accordance with the procedure laid down by the LBMA (see Annex G “Weighing, Packing and Delivery Procedures for Gold and Silver Bars”)
Shape: Bars must be cast in open moulds and be ingot-shaped (i.e. with the top surface larger than the bottom surface). A bar should be produced at a single pouring so as to avoid any layering. Bars must be easy and safe to handle and convenient to stack with, in the case of gold bars, the larger (top) surface showing the marks and in the case of silver bars the top surface or end of the bar, as detailed below, showing the marks. It is important that the edges of the bars must not be sharp, so as to avoid the risk of injury during handling. As from 1st January, 2008, the use of closed or gated moulds was no longer permitted for the production of Good Delivery bars.
Appearance: Bars must be of good appearance. Faults that must be avoided, especially on the top surface of a bar, are 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) and excessive shrinkage (i.e. the concavity of the top face of the bar and any concentric cooling rings must not be such that it makes it difficult to either apply or read the bar marks or in the case of concavity bars become unstable when stacked on top of each other). The sides and bottom (smaller) surface should be smooth and free from cavities, lumps and layering.
Marks: Gold bars must be marked on the larger surface (the cast surface at the top of the mould) of the two main surfaces of the bar. This is the surface that would normally be uppermost when the bars are stacked. Silver bars may be marked on the larger surface of the two main surfaces of the bar or on the end of the bar if marked using a dot matrix (pneumatic punching) method so that the marks can be read from the top edge downwards (see attached Annex K). The marks should include the stamp of the refiner (which, if necessary for clear identification, should include its location), the assay mark (where used), the fineness, the serial number (which must not comprise of more than eleven digits or characters) and the year of manufacture as a four digit number unless incorporated as the first four digits in the bar number. If bar numbers are to be reused each year, then 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 then the year of production must be shown as a separate four digit number.
Marks should be clear and the height of characters used should be a minimum of 12.5 mm. Marks may be applied to bars either by using conventional stamping or by dot matrix (pneumatic punching), provided always that if pneumatic punching is used the marks must be no less clear and at least as durable as if conventional stamping had be used.
Weight Stamps: It is strongly recommended that weights should not be stamped on Good Delivery bars. The reason for this is that when bars are weighed in London by an LBMA approved weigher their weights, which may be different, will prevail, and also any adjustment to the weight of a bar caused by future handling or sampling would necessitate alteration to the mark. If bars are so stamped, the unit of weight must be shown.
If bars are delivered in to the London market and the recipient vault is of the opinion that the bars do not conform to the above requirements the recipient vault may ask the LBMA to appoint independent inspectors to examine the bars and express an opinion as to whether the bars are acceptable for Good Delivery purposes. For the avoidance of doubt, any proposed recipient of bars has, irrespective of any view expressed by an inspector on the condition of a bar, the absolute right to refuse to accept delivery of a bar if its vault manager considers that the bar does not meet the Good Delivery standards as set out in these Good Delivery Rules.
Source: Bullion Bulletin