sidemount covers anyone?

Hi- I have a nice pair of sidemount covers but do not know what they fit. I bought them for my '31 Pierce but have found another set. These are unique in that they have a t-handle on front and back of each cover, each of which tighten a clamp on the back of the sidemount. Opening is slightly less than 19 inches, outside diameter about 33 inches. Think this fits a 650, 700, or 750 x 19 tire. Any ideas, are they specific to a make of car? They are surplus to my needs at this point.