Paul — You might be surprised by how many members of the public notice things like stopper numbers. I can't think of any reason to distinguish glass collectors and dealers from the public in this respect, save for the fact that collectors and dealers are likely to examine an object rather more closely.
Chris — I didn't say it was a stopper number, just that it probably was. It could also have been a glassmaker's number for allocating piecework remuneration after annealing, stoppering, and decorating; or an inspector number showing that it had been passed for sale.
Had it contained a smooth island malt, I would have regarded it as a good excuse to finish off the contents before checking the base.

Further observation:
Notice that the "1" in "18" is not a Continental "1".Bernard C.

ps — hope you like my punctuation!
