It will say XP or XPW on the serial tag. The decal on the started also said XPW. Not all 372XPWs were 75cc. The decal on the top cover will say what the displacement is.
The “XP” is husqvarna’s marketing for their pro line. I think it means Extra Power. They also amend a suffix of “G” for generator, which provides power for heated handles. (This letter designation was created before all the modern auto-tune saws which come with a generator anyway which powers the carb-computer.)
They also append a “W” designation for “wrap” handle. Some (in the US) also think of it as “west coast”, since in addition to the wrap handle they also come with bigger dogs, which are suitable for the thick shag bark of the PNW. The wrap handle allows you to use the saw for felling and dogging in on either side of the tree, which may be necessary since you don’t always have the same options on steep ground.
Getting back to your question, the 390 number plate might show 390xp or 390xpw. Same with the 372. Same with the 395.