Hi fmofmpls...here's the ad and certificate for the mummy ring. The ad came from Chiller Theatre Mag, Issue #5, which was for the April '96 show.

And the certificate that came with the ring I reproduced in B&W so I could keep the contrast without overloading the resoloution. According to the certificate, there was supposed to be an edition of 500 of these made, but I don't think there were nearly that many, since, besides mine, I have only seen one other for sale on ebay, maybe about 5 or 6 years ago, even though the letter by the lawyer on the certificate states that the 500 rings
were present that night in '96...

The lawyers letter describing the process is signed by a Bryan Hidalgo, Attorney at Law. Since it is hard to read in the scan, I'll transcribe some of it here...
"Bryan Hidalgo, an active member of the Bar of the State of California, a specialist in the field of entertainment law...does hereby certify and attest as follows:
On the evening of July 3, 1996, I personally visited the residence of Forrest J. Ackerman on Glendower Avenue in Los Angeles, CA, and was shown a square of gauze material by Mr. Ackerman. It reflected obvious evidence of extensive usage and aging. It was identified as an actual piece of material used by make-up artist Jack Pierce for the film THE MUMMY, and is presently owned by Mr. Ackerman.
I personally inspected the material.
Following my inspection of the fabric, Brian L. Forbes, in a continuous operation occupying a period of almost four hours, took numerous loose threads from the fabric material and placed them into the underside of 500 limited edition sterling silver rings.
I was personally present throughout the entire time that the work was in progress.
Based upon my personal observations and the information which has been given to me as hereinabove set forth, I herewith certify that the contents of the threads which are to be inserted into the sterling silver rings contain actual material used by the character Im Ho Tep in THE MUMMY."
Must have been a fun night at the old Ackermansion! I'll try to take better pics later today.