This may not be relevant but worth mentioning when talking about going through IBM relays with a tester. This bit me bad a couple years ago on a WCR controller. I clean them with the little burnishing sticks from Adams, re-pin and replace as necessary. The newer IBM relay testers that Sees and, I think, Adams sells don’t have a set of LEDs for the N/O and another set for N/C. They use a single bi-color LED that goes green for N/O and red for N/C so they work fine to tell you if the contact is closed or not when it’s supposed to be. But they will not tell you if a contact is closed when it’s not supposed to be so if you get a set of pins crossed up like I did, the relay can test good even though the contact never open.