If S-K would give us the map to their damn coding system we'd know.......they refuse to give it up. I'd put that in the 60's perhaps? Maybe later.
I am an SK neophyte, but the codes on my ratchets are all over the place, with 2-4 characters. This Kraeuter is A, 2nd digit possibly upper case i, number one, or a T with top cut off. The selector is identical to my Dresser-era SK 45170, wider bar than my older Mac X3R. The Mac has plainly visible tooling marks on the selector, others are smooth w/o tooling marks...machined from solid stock vs die cast?
I'm not sure when Kraeuter branded SK drive tools were introduced. Not scientific by any means, but from what I've seen, the I-beam handle Kraeuter rats seem to outnumber this flat style by around 9 to 1, possibly more. I have also never seen a flat handle in a blue hammertone metal set case, but like I said...SK newb, there is a lot I've never seen.
Based on some PM correspondence/conjecture with bbrins on this subject, trusting his input since he owns just about every vintage iteration of SK ratchet ever made, lol.
Bear with my theory...J.C. Penney branded SK rats had a similar flat handle, as well as those with Klein branding (And possibly others I've never seen). It would make sense for SK to streamline production, keeping classic knurling for themselves, while applying contract production re-brands to the flat handle, and discontinuing the mostly unique Kraeuter I-beam altogether in the interest of simplification. Plus, that I-beam is, in my opinion, kinda goofy and not very ergonomic nor particularly comfortable, and I know I'm not the only one with that opinion.
If so, I would lean to more modern production- say late 70s/80s, once again guessing as I do not know particulars about when Kraeuter was shuttered, or when J.C. Penney models were dropped. I have seen presumably even more modern Klein re-brands with knurled grip, assuming a further simplification to only one style handle at a later time.
Another clue is the part number, a 3/8 I-beam Kraeuter was no. 32070, the flat being 32071. This numbering scheme appears the same in 1/4 and 1/2 models, a literal one-upping across the board. To me it seems like a Revision 1 on a blueprint. I can't imagine both models being sold simultaneously, I've read Kraeuter was a 'value' brand of SK, would seem strange to offer handle options on the value brand and not the flagship brand.
One last thing, the stamping on I-beam Kraeuter rats seems to be a closer match to that on older SK, with smaller stamps and occasional 'character flaws.' The stamping on the flat handle is very nicely done, well spaced, took chrome evenly, and the font seems more modern to my untrained eyes.
Again, this is basically just me thinking aloud. I welcome suggestions.