As far as my knowledge goes, silver coins are obviously a lot softer than the alloys that we use today, and between the late 1700s-mid 1800s there was all manner of problems with keeping enough new coinage in circulation which meant that heaps of old coins were kept doing the rounds far past their use-by date. Whereas today I suppose coins that are too worn are taken out of circulation by the banks, they couldn't afford to in that early to mid 1800s time. That's why we get tokens, pretty much people taking the coinage problem into their own hands. I think it all got sorted out more or less by the 1860s-80s.