ceco joists
i have an old "ceco" catalog from 1967, but it doesn't specifically relate the info on the tag to a particular joist. i can fax you the sheet if you give me fax number. you may be able to determine what each number or letter on the tag means by some assumptions.
ceco corporation is now owned by new columbia joist company (800- 631-1215). they may be able to help you identify your joists.
i've had excellent experience with contacting the steel joist institute (sji)direct. just call them and they should give you information on how to measure the existing joist. then they should give you the sji equivalent capacity for that joist. this should get you in the ballpark.