Put in a Woops Factor for S&W...there are more than a few of the 10-5's with HB's...
MFR's have been known to "misplace" a box of frames and find them a few years later...
then simply assemble them with current components and ship 'em out like normal...
note that S&W frame numbers were shipped out of sequence a LOT...that's why there are no Specific Dates, just general guesses...
Say a guy stacks a bunch of 10-5 frame boxes next to his station on Friday, and at the end of the day has one box left...
so Monday, he calls in sick, the cover guy picks up the one box and puts it under the workbench or replaces it in the wrong place...
a couple years later, someone finds the box of frames and asks the boss what to do with it,
or just decides "Hey, we're doing 10-6's, which aren't any different except the barrel..."
Humans are humans
How else can one explain a NIB 1960 Marlin 99-G with a gold trigger & walnut stock that neither should have been on it??
Someone on the line runs out of a part, then grabs something that'll fit instead of stopping the line...
maybe on a Friday close to quitting time someone took a shortcut...or had one left over & didn't wanna take it back to the shelves...
ya never know