Warbird Information Exchange

I bet that's a period between the K and N - so: K.N.-1 (like in the T-6 Texan in Action photo caption above).

I hate to be a nitpicker, but that's exactly what it says in my post 7 posts before yours.
Doug

This shows how bad my memory is getting. The magazine in question was Aero Digest May 1953, not Popular something else!
The aircraft in question was T-6F (identical to an SNJ-6, which I called it earlier) 44-81691 (6147th TCG, 6148th TCS) which crashed into the sea E of the 38th parallel Dec 17, 1950, with both crewmen rescued.
The article makes it clear that the float was home grown, not rescued from another aircraft type, and was initially installed 2" too far forward. This was corrected after some tests.
Designated KN-1 by the Korean Navy, the aircraft was used in an anti-smuggling campaign for several months before a fatal crash near Chinhae naval base in late November 1951.
cheers Doug

I took a better look at the 2 photos with the letter codes . I think the old lettering is TA-691. And since the 3 numbers are the last 3 numbers of the call sign/serial number (as with the a/c below), the s/n of the T-6F is 44-81691 (6147th TCG, 6148th TCS), which crashed on Dec 17-th, 1950.
The color photo obviously shows different letters. They seem to be K?N.-1. The plane was designated KN-1, but there is a vertical bar (like in F or P) between the first letter (K?, but also possible A, R, X) and the last N.
Could it be KFN.-1?

They seem to be taped over USAF lettering--TA-69Y?.