I recently purchased a (used) Toyo 45a, and it seems to be jammed closed. The baseboard release button is missing. I've tried using a pencil eraser to press where the button should be with no luck. I've done some additional fiddling, but I'm worried I'll break something. Any insights on how that button works? I'm thinking I could insert a paperclip somewhere and loosen something, but I don't want to tear the bellows fishing around...

I'm a newbie to all things 4x5. Thanks for any/all help!