While this question doesn't really fit the timeline of this category (1965-73), it is non-Mustang Ford related. The only other category I could think of was the "Lounge", and I was afraid that being there with everything "under the sun", this would not get to those who might know the answer to my question. In the last 3 plus years that I have been participating on this Forum, I have found that there are a lot of people who have either worked for Ford in some capacity, or know people very well who have. It also appears that their knowledge and the experience that comes with it, extends beyond our "Mustang Years". It is this knowledge that I need to draw upon.
Prior to getting my first Mustang (a 1966 Coupe) in 1976, I was. and still am for that matter, "into" mid to late 50's Fords; specifically Retractables, Rancheros and Thunderbirds (I have a 57 and 59 Retractable, a 59 Ranchero and 57,62 and 66 Thunderbird). My Dad purchased the 57 Retractable as its second owner in 1961, and I bought it from him in 1963. A year or so later, I learned how to rebuild my first Y-Block. I "blamed" my Dad for that for years because of the way he drove it an particularly on Vacation in Eastern Michigan in 1962, when he just had to show my Sister and I that the 245 hp 312 Retractable would in fact bury the speedometer at 120 with the top down on the way to Traverse City.
In late 1964, sure enough, one of the main bearing seats cracked, the crank broke, and two rods went through the cylinder walls. At the time, 312's were in short supply, so I had to settle for a 292, and bored it out and built it up (15 years later when I decided to restore the car, I did come up with a true 312 and rebuilt it; it still remains in the car).
The 292 that I picked up at a yard, had a cardboard tag about 2-1/2" in diameter bolted on by one of the water pump bolts, and with cut out (stenciled if you will) numbers on it. I asked my Ford Parts man at the time, but he had no idea what it meant.
Through the 80's, and early 90's, I became very active in the International Retractable Club, becoming its Technical Editor for quite a few years, and even writing about 60 pages on the Marketing and Collectibles of Retractables for the book "Birth of the Retractable" which was co-authored by the Club and Ford's original designer of the Retractable, Ben Smith. During my time of heightened activity with Retractables, every once in a while one would see one of these cardboard tags. Even then, with all of the contacts, no one seemed to know what they meant, or how to decode them. As frequently happens with the passing years, this item became a "sleeping dog".
Then in 2006, when I finally got a '57 Bird (to go along with my 62 and 66's), the tag issue was resurrected. Both Thunderbird Clubs (CTCI and VTCI) show pictures of them in their Restoration Manuals, and both note that "More Information is Needed and will be Forthcoming". Well, none of the "guru's" in either Club have yet to explain this tag. It has "commonly" been called an "Engine Foundry Tag", and is even being reproduced (all with the same stenciled number of course, and a much lighter material than the originals. It is also widely accepted that these were only used from 1955-57, and show up on 6 cylinder engines, and 292 and 312 V8's. I recently came across one on a 292 in a yard in Southern Colorado, and a friend found two on 292's in a yard near Mesa.
I have attached pictures of ones shown in the two Restoration Manuals, one that was listed on Ebay, as well as the one I found recently. There appears to be no correlation to the VIN number, build date or unit number.
Hopefully, one of you with "Ford ties" can help solve this mystery before there is no one around that can.
Thanks for reading this, and hopefully providing some insight into this "mystery".