The letters that you refer to are the letters that are designated by the Coast Guard to identify builders.....as stated before, the Cigarette letters are CRT....so not knowing for sure, but taking a guess, I would think that your boat is probably a P&D made boat.
There is a history of the 24 on the banana site...
www.bananaboatco.com
Go to products, then click on 24 then scroll down and click history of 24. It basically tells of a special boat that Don and Carl Kiekhaefer made for Doc Magoon 24 by 7 with outboards. Magoon didn't like it so they made a new one with 24 by 8. He liked it so much Don made it part of the Cigarette lineup. Once Don released the 7 foot molds, everyone made a splash of them and you can see many builders made the same model.
They have been made for many years and are good boats.