Your bullets are Lyman # 410610, a semi-wadcutter gas check bullet that nominally weighs 210-215 grains.These appear to be lubricated with the original "Lyman lube" which is a moderately hard wax based lube with a lot of graphite in it resulting in the black color. They can be loaded without the gas check, but you should clean the lube off of the gas check heel before loading.

If you stay away away from maximum listed loads you can simply use any load you find in any manual for a 215 ge cast bullet or 210 jacketed. To worry about a specific load for this specific bullet you are way over-thinking the process! If you want to be that specific go to the Lyman Cast Bullet handbook and look up a load for 410610.

Or to keep it simple just use the 7-8.0 gr Unique others have recommended. With only the few bullets you have you are hardly going to "Work up the best load" for them before they are gone!