Experimental Airworthiness

I just purchased a glider that has a Special Airworthiness Cert.,
Experimental Category, Exhibition and Racing. The "Date of Issuance"
was 5/6/1983, as was the Operating Limitations and log entry. To the
right of the Issuance date on the certificate is the "Expiry" which
shows one year later as 5/5/1984. The operating limitations makes no
mention of an expiration, in fact it has the paragraph stating that
"no person shall operate...unless condition inspections are done in
the preceding 12 months" (which would be for the second and future
years), and it mentions condition inspections (plural) are to be
recorded. The entry in the log by the same FAA Rep. makes no mention
of an expiration.

This would have me think that the intent of the FAA representative was
to make the certificate of unlimited duration as I would expect. The
FAA database also shows no problems that I can tell, such as an
expired airworthiness certificate. Is this typical to have an "Expiry"
date on the cert. or do I have an issue? I hate to lose my loose
operating limitations by having to apply again. Can anyone explain?