Four-Inch Cobra - - -
- - -All I've ever seen had the square butt, so that they looked just like the then-current Police Positive Special, except, of course, for the light weight. I understand these were popular in Latin America, and have heard of some with military or police markings.
My reference indicates LW-13XXX was produced in 1952.
The only three inch Cobra I ever had was the round butt version--Never saw a two- or three-inch with square butt.
In a a lot of times and places, sidearms were worn largely as status symbols. I read of at least one U.S. firm with remote facilities in Latin America which required their personnel to carry, to discourage theft and guerilla attacks. A four inch Cobra, or, say, an airweight M&P (later M12) with four-inch barrel, has advantage of appearing to be a more-or-less "full size" revolver, and yet less of a burden in day to day wear.
The "+P" rating is fairly recent--There was no such thing when the Cobra ws introduced, and probably still was not when the four-inch was discontinued. There were some "High Speed" and .38/44 loads, which would qualify as +P nowadays. And, like the +P, they would have loosened up the alloy frame revolvers pretty quickly.
I agree with dfariswheel - - - I'd shoot your Cobra with target or standard velocity loads in practice. I would have no qualms about keeping it loaded with +P for home defense. No single +P, or 20 of them, will blow up a Colt or Smith alloy frame piece, but it WILL dramatically accelerate the wearing-out process.
Almost forgot - - You asked about worth. Hard to say, properly. The four-inch, though scarcer than the two-inch version, is not nearly so popular. Several years ago, I saw two- and three-inchers going for $135 to 150, in good to very good condition, and their four-inch brothers for under $100. Times have changed, of course. I would offer $200 sight unseen for yours, in the condition you describe. It is probably worth more, naturally, especially with original Colt stocks.
Best,
Johnny