The second scale sounds like a good Idea till you mess up everything due to using the wrong one. I once had a Spirit Level that was for plumbers and had a Second bubble-level built in that was even when the Level was tiltet to about 1.5 degree, great for waste-lines and gutters. Now everything in my House ist tilted by 1.5 degree except the plumbing and gutters.
The second scale sounds like a good Idea till you mess up everything due to using the wrong one. I once had a Spirit Level that was for plumbers and had a Second bubble-level built in that was even when the Level was tiltet to about 1.5 degree, great for waste-lines and gutters. Now everything in my House ist tilted by 1.5 degree except the plumbing and gutters.