At one point in time Towmotor stamped the serial number into the front frame crossmember plate up near the top. With the serial number any Cat forklift dealer can tell you the model number and capacity range. If you need to replace the master cylinder, the master cylinder casting should identify who Towmotor was purchasing the cylinder from. The manufacturer name should be cast into the side of the cylinder along with a number. Two common suppliers were Wagner and Bendix. Take the cylinder to your Cat forklift dealer or any good parts store and they should be able to find a cylinder that will work. You may have to adapt some fittings.