Woodworking Bench Vise (Bray SL6)

Record 53 bench vice with 10.5" jaws
This from memory was made in the 1930s and was the first model with the quick release lever. The weak point was the lever return spring which was not robust enough and would break. Later versions had a completely different arrangement.
I played around with replacement springs but couldn't find one that was just right either too soft or too hard.
The vice still works fine but the quick release sometimes doesn't work properly