So I'm looking at my brand new (to me) old Beseler MCRX 45. I know this is a common enlarger, but I have never owned one, till this orphaned fellow. It's pretty strait forward of course, but a couple of questions. Directly beneath the condenser, but above the carrier, there is a slot that contains a large ?holder? long D shape dealy that has a scratched up piece of plexi in it. Is this for giant contrast filters? or a place to warm a ham and cheese? Above the lens board there is another, smaller holder that looks like it is made and sprung to hold glass filters. Where can one obtain filters to fit this, or what is the current vogue? Thanks.