The registration # on the 12's is at least a 3 off, Neal. Mine, Pauis and my friend in Singapore. All pencil shanks, all stems like Paul's. (from his post in the other thread.) Mine has the two tone funed top finish reminescent of those days (which Castello does on other shapes
as well from time to time.) So, as you imply, the stamp does double duty, trademark protection and a nice touch for collectors.
I am reminded of the white stem/black dot Castellos. Back in the 1990's, word got out that these pipes existed and were rare because they only made a few to keep the trademark alive. I saw a Sea Rock change hands at a show for more than US full retail new (at a time when most new Castellos came in at a discount on the grey market) and it had been smoked. Every Castello collector in the country wanted one. The then US agent explained this to Franco Coppo, and within a year or so everyone who wanted one had at least two. Including moi.
BTW, Bollito has one now, but with the longer stem that was also used in those days. But apparently no registration #.
Bollito 12