Are you sure the lenses are 3.5"? As I recall 451's were what we called "Baby" Appletons, much shallower head and were all marked 451. I think what you have is a later (60's) Appleton offering. I had a set on my 56 Merc that were the same size & appearance as what you have but were not marked and marketed by Cal Custom, these had Appleton style handles and were fully functional. See the attached advertisement. Mick
These we're purchased by my grandfather in '57. The housing is roughly 4.5" the lamp approximately 3.5"
Those look exactly like the ones on my 56 Merc. I think the Hot Rod Mag article had the size wrong, and was no doubt earlier tan the 60's, which was only my estimate. They have the same shape as what are now called "Dummy" spots, but were fully functional. Here's a pic of my old Merc taken in about 1960 or 61 at a show in SLC, showing the spotlights. Mick