in the light of Phelps Warren's comments (1981) that ..."The piggin is essentially an Irish vessel; it does not appear that it was ever made in England." - then this post should be in British & Irish, but not entirely sure so have posted here, but the Mods. can of course move if wished.
Rather crude and basic cutting - not remotely likely to make you think of Ireland, but the depression under the base is wide and shallow and together with the amount of wear, then might suggest 1830 - 50, but for all I know could be later.
Those examples for table use, were apparently larger than this one - over 7 inches (175 mm plus) is not uncommon, but Phelps Warren also discusses miniatures down at about 4" (c. 100 mm), which is the exact same height as this one.
Definitely not lead glass, and one or two seeds with single small black stone.
All thoughts welcome - is this a miniature piggin, a prentice piece, or made for some other size-related purpose - an unusual punch ladle for example.
Thanks for looking.
Ref. 'Irish Glass' (Revised 1981 edition) - Phelps Warren