The manuscript dictionaries occasionally refer to sums of money when providing example forms related to trade, and this can be confusing for anyone who is not familiar with the currency units and symbols in use at the time. In this section we provide some guidelines and notes on historical currency.
The currency system of the Ancien régime in France used a set of units which are similar to those used in Britain until the 1970s, and in fact often notated using the same symbols, as well as a range of other units/coins which changed over time. These are the most common:
| Unit | Symbol(s) | Equivalence | Notes |
| livre | £, L, L., Liv., ₶ (livre tournois) | 20 sou, 240 denier | There were multiple livres in use in different areas, including the Livre tournois and the Livre parisis. Each of these had their own associated sol and denier divisions, so the values of these units also varied geographically. |
| sou | S, S., s, s. | 12 denier | Originally from Latin solidus, dating back to 4th-century Rome. |
| denier | D, D., d, d. | From Latin denarius, a unit dating back to Ancient Rome. | |
| écu | V., W. | 3 livres | Created 1253. |
| louis | 3 livres / 20 sous | 1640-1795. | |
| franc | 1 livre | Created 1360. | |
| gros tournois | 12 deniers / 1 sou | Created around 1260. | |
| liard | 3 deniers | 1564-1792 | |
| double tournois | 2 deniers | Created 13th c. | |
| maille | 1/2 denier | Created 12th c. |
More detailed information on currency is available here, and on abbreviations/signs here, where some useful hand-drawn symbols also appear.