The Dialogue, and books based on it, make much of the process of assaying coins brought to the Treasury, and the distinction between blanch and tale payment. This implies that the coinage in circulation at that time could be made of silver of dubious purity. Assays were needed to ensure that payments made were equivalent to the required quantity of silver of the correct standard.
By the thirteenth century, this was no longer such an issue. A number of recoinages, and strict control over the mints, meant that the silver penny, the only coin in general use, was produced to a consistent and reliable standard. The problem then was not the purity of silver, but loss of weight, by wear and clipping. The distinction between blanched and numeric payments had fossilized: some payments were described as numero, meaning a straightforward cash payment of that sum, by count of the coins delivered; some were described as blanched, which meant only that they were subject to the addition of a shilling in the pound, or 5 per cent. Calculations within the rolls show that conversions were done on that basis:
Et restant ei locande lxiij li. et iiij s. et v d. bl. qui sunt ei extensi ad lxvj li. et vij s. et viij d. num. …
[£63/4/5 = 15,173 d. Add 5% = 15,932 d. = £66/7/8]
Samples of coins were still assayed, to test for purity. The results were noted in schedules of combustions, some of which survive as attachments to Chancellor's rolls.