I don't think they are proofs or were issued when the N173 cabinets were. These types of cabinets only seem to mainly exist for Omaha players. It also seems like most (but not all) of the "N173 Proof Glass Negatives" are of Omaha players.
Not sure why Omaha, but I don't think they are contemporary to the set being distributed.
Last edited by packs; 01-24-2014 at 10:41 AM.
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