A serial number like IB3523 means it's a very late model
The engine serial number CE 203474 PA agrees
Some information on the IB
Having not been run in about six years I cleaned the air cleaner and put new oil in it, then took the plugs out and put in a bit of oil in each cylinder and spun it over a few times while checking for spark which worked nicely. Then it was to put some gas in it and put the spark plugs back in and it took off and ran like new.
Now I have to decide what to do with it