Now that is interesting neither one of mine have that window the question is is it because mine are 2 plays for 5c or is it earlier or later machines the serial numbers on mine are 3015546 and 301561, I just started a total rest on 301556.
I just looked at some pictures of Daves 2 plays for 5c slot and his also had the access panel so I assume it must have been an early verses later production change, I wonder if Dave still has the serial number from his machine?