Thanks darrsi and bbrown1664. The pipes are all welded with no separate sections, I'll give them a proper clean up to see if there are any faded markings. The outlet diameter is 45mm and they're in sound condition, if the silencer is beyond repair at least I have the outlet size to go off for replacement. The combination of the pipes and silencer has the engine running nice and smooth, very quiet (maybe a bit too quiet) but I wouldn't want to upset the balance for a bit noise.