As noted,, the original emblem was designed by Alex Sturm. It was a recessed eagle,, no "SR" in red, with the raised outer portion silver. When he passed,, the color of the "red eagle" was changed to black in honor of Alex.
For many years,, it was that way,, with a few minor modifications. Early ones had what we collectors call the "skinny neck" on the eagle,, which later went to a bit fatter neck. then in 1967,,, for a short time,, the eagle got "neck feathers" but the eagle was still recessed, and black.
In the early 1970's,, the emblem was changed.
The eagle got raised,, while the background was recessed. AND,, the eagle was silver,, WITH the addition of the SR in the center of the eagle, and the background was black. That too has been the basic standard for decades.
Yes,, there have been variations,, due to vendor differences,, such as the mid 1970's era where the eagle was what we call the "squashed chickens" type,, where the actual eagle was not as defined as others. But it was still a silver raised eagle,, and the background was black.
And as noted,, there was another change in the background color where the background was red,, and the eagle was silver. It started with the MK series guns,, initially on the magazine base pads at first if I recall correctly.
But in the 1990's,, & early 2000's,, we have seen it spread to other models,, but it remained a silver eagle & either a red or black background. Model dependent. You can find both.
When they introduced the "retro" Flattop New Models,, and the slightly different XR3 grip frame,, they returned to the black recessed eagle,, NO SR in the center, with the raised area silver. Darn near identical to the original design,, from the early 1950's.
And later on, they made another change,, they went from the raised silver eagle WITH the SR in the center of the eagle, to the "R" not the SR in the center.
And then we have the smaller,, medallions,, for the Bearcat & the Red Label guns. One color,, silver for the Bearcats,,, and gold for the Red Label.
I'm sure I may have missed a few details,, or a little off on the dates,, but that's a little bit of the history of most of the medallions. But a true original red recessed eagle,, with the raised silver outer,, like the very first ones has only been done on the special One Millionth engraved Standard Auto as far as I can recall.
In short,, the medallions have had several variations over the 75 years.
And some folks mistakenly call a red backgrounded medallion a "Red Eagle" type.