Identify a Thyristor
I am not as pessimistic as others regarding the viability of an old thyristor. If it is not shorted, there is a good possibility that it will work. These devices are either good or obviously failed.

It requires a substantial heatsink. A little terminal attached to the stud as shown in your picture is not sufficient for any significant use. The heatsink shown below was designed for blower cooling a similar device.

Cross Reference:

I found information to indicate the C50F is a 2N1910 rated 70 to 110 amps, peak repetitive off-state or reverse voltage: 50 volts.