The casters are the best indicator that its a P-20. The P and C models have dual double casters and the H model has a dual single casters.
If you go look at it check to see how wide the blades are. This is the reel off the 27" model I bought and my repair shop is not sure if he can sharpen it or not, I'm going to replace the reel, but thats about $400.
You can see where the blade is welded to the disc that is welded to the center rod. Make sure the blade is a good 1/2" or so past that disc, mine is around a 1/4". I'm still a rookie to reels but I've messed with mine enough to have learned a little. Could the reel in the picture be sharpened? I'm not experienced enough to know for sure, I'll have to take the shops word for it.
Ask the owner to demo it for you.
Tru cut's are nice, but they are a pain to adjust. If you're a mechanically inclined person you'll be ok. If you don't like to tinker you might want to look at a Trimmer or McClane. I love my TruCuts, the ability to feather the clutch and control the speed and the center diff that makes turning corners a breeze. But there are things that I hate, mainly the reel to bedknife adjustment. It has gotten easier the more I do it, but its still a pain.