Lead tokens were used in Britain from the late 13th century to the mid 19th century. Until the 1500s most tokens were made of pewter and tended to be small sometimes as little as 11mm. From 1500 size increased to 15-17mm and up to 25mm in the 19th century.
I thought I'd found a led token, but it turned out it was a 19th century cloth seal, I'll update with pictures when I hopefully find one.
Each token was made and used in a specific geographical area, as such there is no uniformity or standard conventions and tokens with a diverse range of markings were produced. They appear to have had a number of functions.
The production of coinage was controlled by the monarchy. From medieval times high production costs meant there was little incentive to produce 'small change', leading to a shortage of smaller denominations, a situation which persisted for centuries. The smallest coin was a fathing, equivalent to a few days wages. Ordinary citizens needed lower value coins for everyday living, so local communities came up with local solutions and created their own unofficial currencies in the form of lead tokens.
Their underground status means there are few records of who made them or how they were used. It is summised that some were used as money, others were used as passes and some could only be exchanged for specific goods or services. Attempts to prohibit their use in the 16th century seem to have had little success, Sir Robert Cotton, lobbied for action in his paper entitled " T h e Manner how the Kings of England have supported their Estates," addressed to King James in 1611
" The benefit of the King will easily fall out, if he restrain retailers of victuals and small wares from using their own tokens ; for, in and about London, there are above three thousand who,one with another,cast yearly five pounds apiece of leaden tokens, whereof the tenth
remaineth not to them at the year's end, and when they renew their store that amounteth to above .£15,000 ; and all the rest of this realme cannot be inferior to the city in proportion. For the prejudice, since London, that is not the twenty-fourth part in people of the kingdom,
had in it, as found by a late enquiry by order of the late queen, above 800,000, so falleth out to be two pence each person in the entire state ; may be nothing either of loss, by the first uttering being so easy, nor burthen any with too great a mass at one time, since continual use will disperse so small a quantity into so many hands ; but, on the other side, will be of necessary use and benefit to the meaner sort, except the retailers, who made as much advantage formerly of their own tokens, as the King shall now ; for the buyers hereafter shall not be tynd to one seller and his bad commodities, as they are still, when the tokens
hereafter made current by authority, shall leave him the choice of any other chapmen ; and to the poor, in this time of small charity, it will be of much relief, since many are like to give a farthing almes, who will not part with a greater sum." British Num Society