The space saver spare tires were available in Mavericks from 1975 to 77. They look just like the photo Ratio411 posted of the Mustang one. That one has probably been repainted since they came with a decal which included use instructions and a special metal valve stem. In 1976 they were a $13.00 option on cars equipped with bias-ply tires and a no-cost option on cars factory equipped with radials. They came with a special bracket which held the inflator canister. They are VERY hard to find, and the canister bracket and inflator canister are really hard to find too. I have one NOS setup with all the pieces but no photos to post. Sorry.
Then I THINK yours is actually a Mopar or AMC unit. Check the instruction decal. It will have a Ford part number on it if it's a Ford one. If memory serves, the other brands will have a white decal instead of the yellow and black Ford decal. That's assuming it's all original, of course.
They were available on Mavericks, I have the original owners manual for mine and it has a section on them. If they were listed that early and are still listed for the 77, they must have been real.
Related, but a little off-topic... I got tired of a full sized tire taking up a 1/3rd of the trunk of my Comet. Found a nice narrow spare for a mid-80s LTD at the junkyard. It has a 5 bolt 16 inch wheel in it, is almost as tall as a regular tire, but is maybe only 5 inches wide. Got a bunch of trunk space back, and you keep it aired up tight, so no worries if you ever need it.
I've got one in the garage that came out of my Dad's 72 Mach 1. It has a white sticker on it with black writing and D2 part number. I'll take a picture of it tomorrow to post. - Matt
