And what might that number be. ?
SA boxes usually said so on them ?
Looks to be for a lightweight (?), so its not going to be of immense value.
Looks to be in very good order.
Tricky to identify from that view, not the usual angle you see them from.
A head on view of the business end of it may be more helpful ?
Its a chaindrive/belt drive specimen, obviously,
There were quite a variety back then, names mostly faded into obscurity.
Are you in the UK or europe, that may have some bearing on its origins,
and are the fasteners imperial or metric.
Someone familiar with this variety will hopefully leap in...