Of two detachable carrying handles I'm looking at, one with a Split-A and "A" on the left side is the commercial height. The other with a Split-A and "B" on the left side is the mil-spec height. There's also a Colt branded Square Forge and Cardinal Forge one I've found being the commercial height.
To identify without a caliper, a person can just use a ruler to measure the rear shelf area. It's about 20mm from the bottom to the top for commercial and 21mm for the mil-spec. The area of note is below the roll pin that secures the elevation knob. After a while, you can tell just by looking. If it's the commercial version, you'll see that space is just under 4mm with the mil-spec being just over 4mm.
Seems the military could have forgone the whole 'F' marked FSB and stuck with a regular A2 FSB and combined it with the lower height detachable carrying handle. Maybe that would have alleviated some of the confusion.