Hello All, many thanks for your replies and recommendations. I've just looked through the Armours listing and can't find a model that states alloy, rigid, and includes the year 54.
Feked have a few for rigids, with alloy head, but the wrong years
"AJS/Matchless Exhaust Pipe 18, G80 Alloy Head, 500cc 1949-52 - OEM: 018139"
Or this one, but it's 55 on:
"AJS/Matchless Exhaust Pipe 18S, G80S, G80, 18 - 500cc 1955 on"
And, this one, but in the detail says for comp machines
AJS/Matchless Exhaust Pipe Rigid - Alloy Head 500cc 1950-54
In the AJS 1954 Spares List it gives 018139 for 18 and 18S for the pipe, and 014576 for 18 and 18s for silencer. These numbers are available from Feked, as:
AJS/Matchless Exhaust Silencer 18, G80 Alloy Head, 500cc 1949-52 [OEM: 014576]
AJS/Matchless Exhaust Pipe 18, G80 Alloy Head, 500cc 1949-52 [OEM: 018139]
Nothing seems to match up.