I've never seen or owned a Savage or Stevens 24 with a barrel-opening release in the front of the triggerguard - IIRC, that's a feature of one of the Brazilian break-open designs (Rossi ?).
ALL early Savage & Stevens 24's had the side barrel selector at one time - then, in the 70's IIRC, Savage introduced the hammer-top barrel selector because they thought it a better/stronger design than the side selector.
In the late 70's, Savage stopped suppling the side selector parts as a repair item, sending the entire new-style hammer to side selector customers who ordered a replacement for a broken selector.
It seems that Savage got out of the business of supplying side selector slides - which had a very high percentage of breakage, right at the 90-degree turn the selector makes to pass through the receiver wall into the selector button.
I've used the both, and prefer the side selector as esthetically nicer, and easier to operate for me (YMMV) - especially these days, when aftermarked side selector slides/parts are readily-available (
www.savage24.com )
These are a Stevens 22-410 Tenite, and a Savage 24-B .22lr/.410 - both too early to be a hammer selector (1939 & 51).
.