The good folks at Screen Used props have Commodore Decker's TOS Insignia up for sale in a very nice display case for $ 3,999. The description reads:
"These original series artifacts were screen worn by Commodore Decker and Captain Tracey in the episodes titled "The Doomsday Machine" 1967 and "The Omega Glory" 1968. This set of rank insignias are very rare costume accessories, as they were custom made for filming and only worn in these two episodes making these a must have for any collector of original series costumes and props. Both came directly from the Bill Thiess estate when his collection was sold at Butterfields & Butterfields. These pieces are presented in a custom display case measuring 16" wide x 13" tall x 9" deep."
A very rare and collectible prop, but at this price and in this economy, I don't see these selling quickly.