Most compressor companies do not build their own pressure tanks because any pressure vessel sold in the US has to certified. Certification is a tough and onging proceedure best handled by specialty companies. The information on the tank is specified by the goverment and does not include the size. Most compressor companies will include the tank size on the tag that includes the model and serial number of the assembly. It looks to me to be an 80 gal. tank, but just a guess. Nice unit, by the way. Two stage with intercooler. If it is yours, you're a lucky guy.