http://www.aidan-campbell.co.uk/Pewter_Guide.shtml

Accourding to this authority, (see blue clicky above), there is little or no lead in pewter drinking vessels. So you can use them for any drink you care to imbibe.

As for the glass bottom, I was always told it so that you could see if you were being tricked into 'taking the Kings shilling'. Fact or fable?