The way I see how things unfolded is as follows, police already had a sound moderator in their possession prior to the 30th August 1985, and on THAT date, police submitted THAT sound moderator to the Lab' under the exhibit reference of DB/1, lab' item number 23...
Inside THAT sound moderator is found the all important, all encompassing flake of blood group activity, A, EAP BA, AK1 and HP 2-1 (exclusive and unique to Sheila Caffell, or so at least we have had that drummed into us). So, why does Ron Cook make a witness statement, dated the 23rd September, stating that a gun silencer handed to him at 9.15am by DS Stan Jones had the exhibit reference of DRB/1, if he is trying to infer that there was in fact just the one sound moderator?
My take on the matter is that because by 30th August 1985, one sound moderator was already out of the possession and the control of police, because it had already been sent to the lab' by the 30th August 1985, and Ann Eaton had later handed in the other sound moderator on the 11th September 1985, which in turn had been fingerprinted by DS Davidson, and DS Eastwood, on the 14th September 1985, and subsequently submitted to the same lab; where the other sound moderator had already and previously been submitted, and by the 20th September 1985 with a note from the police to check the sound moderator in question, for blood, and fibres, it appears that the purpose of Ron Cooks note to Malcolm, was intended by that stage to alter the exhibit reference given to the latest moderator, into DB/1, because police did not want anyone to find out that police had got at least two sound moderators by middle to late September 1985, for obvious reasons...