I met Mark Severin when I was a child . He exchanged material with my father - worldwide collector too . Mister Severin was a talented engraver who made many engravings for Belgian post stamps . As an artist he was not obligatory interested in ugly rare or gem shells . The pure beauty ,the esthetic was his goal . Coming back from Spain my father had a huge lot( some 300)of glossus humanus/isocardia cor , most life taken , all kind of sizes and a few giant ones with the blue points . One isocardia was a dead doublet with coral and 3 fixed life brachiopoda attachment . My father had no intention to sell or trade that peculiar strange cluster . Returning home Mister Severin succeeded in taking the treasure with him . Maybe Charles Geerts or Jacques Senders can tell You more . BBG from PVDB . I do not succeed to enter Listery .    

of course listserv. of Conch-L archives.

"Returning home he succeeded in taking the treasure with him " . In case of confusing message ( english is not my own language ) Mister Severin succeeded of course in persuading my father to exchange the "tresor" - he obviously did not steal the shell .My apology . BBG from PVDB .