1937 16 h seat springs

The only correct answer is 'long enough to bring the rear level with the front mount in use.

Is this a frame with the horizontal spring studs ?

Unfortunately, the only springs that I have here are for the 1936 pattern frame with the vertical studs. I'd happily measure them, of course.

I have a pair off the bike in a box at present. I'll go out and check later this morning.

Picture shows mine.  Note they turn in opposite directions so the saddle doesn't tend to twist when loaded.

I think they were painted black, as far as I can tell from some pictures on Vintage Norton Web site. Maybe someone knows.

Gary, I've measured two machines with springs with horizontal lower mounting studs and both are 6 inches from centre of lower eye to top of spring. Don't know if this helps you or not.

I wonder if mine are squashed by age then?  This is one of the best contemporary pictures I've found with mine also.  It might be possible to scale (from 19" wheel rim diameter perhaps?).  I think they look very similar.  Norton proudly advertised the lower seat height (from 1936?)

...lug fix on Ebay.  (I searched Norton seat Spring).  Just be careful, and as advised by David, get a contra wound pair.  Some of the picture are not.

J