The Seloil brand of oil display cabinets were manufactured by Modern Metal Products of Greensboro, NC. They made them in a number of different configurations. Some designs had either lift-off or roll up doors to cover the cans at night to prevent theft. Some of the cabinets had removable advertising signs in the top or bottom for the brand of oil being sold. Once in a while these signs show up on ebay. The remaining cabinets don't seem to be very common today, and often the doors, signs, or other hardware might be missing. You are correct regarding the drip tray and pan below it. In your last photo, notice the "wings" on either side of the drip tray. On my cabinet, these wings were used to move a mechanism which would lock the other doors closed when the drip tray was slid closed. The key lock would then prevent entry into the whole cabinet. You can get an idea of age from the patent numbers if you have the nameplate. Follow this link to see photos of a cabinet that looks a lot like yours.
http://www.worthpoint.com/worthopedia/seloil-oil-display-rackAlso, if anyone is interested, Matthews Auctions has another type of Seloil cabinet restored in Sunoco colors up for auction on May 15th. Hope this info helps you out.
