Hello,
Hilo is correct, this is a Focomat Ic / Valoy 2 negative carrier that is meant to be used with two glass plates hinged together by a piece of tape and sandwiching the neg to form a dual-glassed negative carrier. Hence missing the silver guide rails, they would hinder sliding in the glass-neg-sandwich. As far as I can tell this is an original Leitz part. That is, i've never seen a thrid party made of this type, so the statement might be considered conjecture. The holder and glass plates are shown in some of the Ic manuals floating around on the web and possibly in the '68 catalogue posted here a while ago. You'll probably find this using the search function.
I believe those where standard issue with the very late grey Ics. I've seen 3 or 4 of those 80s grey ones which came with this carrier. Those late ones also seem to have a silver (not hammertone laquered) knob to fasten the parallelogram on the column. But that's another topic.
I've been using this holder without glass sheets and I prefer it to the older (hammered and laquered) ones as the surface is totally smooth and I've more freedom positioning the filmstrip. It is much lighter than the older ones, something I'm not too fond of. At any rate it works fine with a Ic and Valoy II.
Cheers
Andi