Shoulder Stock???

[Johnny C. Kitchens]

I was wondering if this worth anything today and is it legit. I bought a shoulder stock in 81 or 82, that I always thought was just a reproduction of no importance. I havn't even thought about it since the late 80s. The shoulder stock came in the plainest unmarked blue box you can imagine. Inside the box inside a plastic ziplock bag is a certificate, titled "CERTIFICATE OF AUTHENTICITY AND REGISTRATION", on the left side of the certificate is the "Original Mauser" logo above the address Collector Division, Odin International, Ltd., 818 Slaters Lane, Alexandria, VA 22314. To the right side it has a date of June 5,1981, Stock #666.
Then the main body of the certicate states the following.

This certificate certifies that the Mauser Parabellum Artillery Stock is one of a limited edition of 5000 units. These unique stocks were produced for Parabellum collectors. Limited production of the original Artillery Parabellum stock was authorized by the famous Mauser Werke located in Oberndorf, Germany.

The certificate is signed by Thomas B. Nelson, President.

Anyone else seen or heard of these before? Is it as real as this certficate makes it sound? I will say that it is very well made...