79 CJ-5 Frame number

[JPFever]

Found a number on top of the passenger side rear frame rail. ( J68XXX) The body was replaced with a fiberglass tub.

Any idea what this number means?

[Mr Fast Bucks]

The sequential serial number was stamped on the top of the passenger side frame rail above the front axle rear spring hanger, and above the rear axle.

[JPFever]

Thanks