The SD model, the studs that hold the cylinder block on are on the crank case, later model 102's will have the studs on the cylinder block.This has the copper flywheel cover, aluminium tank mounts and brass air intake trumpet,
the brass trumpet is not fitted in the picture, it has now.
The gearbox has the wartime stamp on the skeg, the older 102's have grease nipples that are for oil,
rather than a filler plug on the front cap,
this type gearbox used heavier weight oil than the later models, parts varied over the years on most if not all British seagulls,
so a seagull may not always be what it seems.
The predecessor to the 102 was the Marston, the early Marston's had a teardrop exhaust and the later ones look similar to a normal 102’s,
as they were designed by the same person and had finned cylinder head.
I think the teardrop version is a beautiful motor and no I don’t own one,
they can be fragile and early parts are very thin on the ground, plus expensive.