The two original fuses are 500V and 50AMP rated, branded as Ferraz Shawmut, PN: A50P50-4
The two new fuses that I used are identical in size, shape, and specification, 500V and 50AMP but they are branded as Eaton (Bussman series) PN: FWH-50B
Basically I called up Platt Electric with the Ferraz...