Bob,
I think what you are seeing is the serial number of the release, not the model number. And as others have said, you do not want to change to a different type of release. Back then, I guess pilots were more interested in flying their planes, so a single tow hitch location worked for both air and ground launches.

Take a look at the pictures of the Tost releases on Wings and Wheels. Look through the papers on the plane. It s probably new enough that it doesn't fall under the "every X years" but falls under the number of actuations limitation.

I would encourage you to not go changing something that is not likely broken and does not need changing.

Just my two cents worth. Enjoy the plane. Oh, I have the Phoebus C that Scott Williams mentions in his note above. I need to get busy on that plane!

Steve Leonard