By the way, some Focomat Ic's do have a filter drawer. You may need to check the enlarger in question. Also, there are two versions of the enlarger head, one round shaped, and another egg shaped. From what I've read on the net the round shape type uses an obsolete bulb type (aka short neck bulb). So, I would make sure that it's got the egg shaped head.
Newton rings may be a problem - they were, initially, with my focomat - but there are solutions for it.
I use a Focomat Ic alongside a Meopta Opemus with a MG diffusion head. I prefer the latter for various reasons, however the Focomat is useful with its condenser (hard) lightsource when using graded paper and the soft light of the Meopta isn't punchy enough.