I'd take a guess at 0 degrees .2 minutes. though measuring .2 minutes is another thing.

in the last post he mentions "no" silver solder, so the removable scope is still feasable.

looking at the set up I'd say the scope is dropped into the rear mount while rotated anti clockwise 30-50°, slid forward into the front ring, then rotated back to verticle.

it must have taken a lot of work to keep the rings collumated when made. that being said i like it better than the A5 mounts that mount to the sight protectors.