It seems to me Glynis Howard dealt with this here too:
http://miscarriageofjustice.co/index.php?topic=169.msg1778#msg1778CAL states DS Jones circumvented internal processes and sytems by entering the silencer into the wrong property book to avoid the silencer coming under the sort of scrutiny it might have done had it been entered into the correct property book.
My understanding is that it was initially given the exhibit number SBJ/1. SBJ being DS Jones' initials: Stanley Brian Jones. It was then given the exhibit number DB/1 being David Boutflour's initials as the actual finder of the silencer. Finally it was given the exhibit number DRB/1 the R reflecting David Boutflour's middle name to distinguish between him from police photographer DC David Bird who shared the same initials for first name and surname.
I always refer to it as silencer as its shorter than typing sound moderator but the names are interchangeable and mean the same thing. Sound moderator is perhaps the correct technical name. Even the judges use both. The fact two different names are used when referring to the silencer does not support the idea there were two or more.