Model 37 circa 1980 S&W CUSTOM shop ?

[model3sw]

I have owned this one about 25 years. I purchased this from a friend of Dad's who was a WWII Vet in Ft. Lauderdale at a VFW gunshow.

SN: J820xxx

According to him, he had gotten this from his son who had recently returned from serving in the US Air Force ... which means NOTHING in extra value unless shipped to a US Military Service. I took no stock in any USAF connection being factual. I just knew someone spent a bundle tuning and smoothing this Model 37 and the price was right. NOW, all these years later, during inventory I noticed a few peculiar markings.

I always knew the red insert front sight on a Model 37 is hardly ever seen. In fact, this is "the" only Model 37 or 36 I've seen with a red insert front on the standards fixed.

I also knew it had an action job, smooth as silk.

I just now noticed unusual marking under the grips on the flats of the grip frame.

Other than the fitment or assembly numbers I found ...

On the right side of the frame (under the grips) there is a " K " inside a circle and a " 5 " inside a heart.

On the left side is " C 19 " and " C26 " clear and clean. with at skewed C4 lower left.

All the above seems S&W Factory stamping as compared to another M37 of similar vintage.

THEN, there is what seems to be a DATE ? 71889 ? July 18, 1989 ?

As I have never seen a factory repair or service mark any newer than the 1970s I am unaware if what I think is a date, is a S&W factory marking.

See pictures below, advise if you can DEFINITIVELY identify the stampings.

Does anyone have a serviced or custom gun with similar date markings.

Please, no speculations or WAGS.

Your assistance is much appreciated. Thank you.

PS: If I were more sure that it might letter nicely, I'd spend the $75.00 for a letter but being the value of this as a nice or customized M37, the cost of the letter is prohibitive on a M37 that is otherwise worth maybe $400.00.