I acquired this no name pipe and after removing the stem, I noticed this possible busted adapter. Not sure…it’s the same exact size as a 3mm adapter.
I tried removing it but it wouldn’t budge… just not sure if it’s stuck or part of the stem. It does appear to have a bit of a jagged end to it.
Could be a non-filter adapter, ( try soaking that part of stem, could be just tar locking it in place ) ? My 9mm pipes(s) come with them sometimes in case you don't want to use a filter and that looks exactly like an adapter.
The tenon would sure be thin if you were to remove the "adaptor. I'd be inclined to leave it. If the rough end offends your sensibilities, just smooth it square with some sandpaper.