Yes Artur, you’re probably correct.
Pictured below is another Buszek made silver tumbler from this same series. Sorry for the poor pics (saved from on-line auction). It has the “Volunteers from France” badge that the PISM “Zeszyt Specjalny No. 1” states is known to have been made in the UK, but does not specify a maker. It also mentions that this was not an officially sanctioned badge.