Search "Hart Razor Bevel" angle on here while you are at it
See assumptions can mess with you, as you are going to learn from the search early Hart razors had a bevel angle that was more in the 13 degree range and many had an issue with holding an edge.. This was improved on as production moved forward, I have not measured a Hart in a couple of years, but again if I were you I would simply measure the angle to see where it is really at to start then go from there..