For First Contact, John Eaves used the 1994 Playmates USS Enterprise-B toy (no. 6172), the only refit-Excelsior-class model commercially available at the time, to construct the golden display models of the ships seen in the display case in the observation lounge of the USS Enterprise-E. He filled one of them up with solid resin, made castings from it for additional copies, and had them all gold-plated
Star Trek III: The Search For Spock failed USS Excelsior transwarp test gifs.
BTW, the transwarp experiment didn’t fail; it was just sabotaged by Scotty. Do you suppose that, after the Enterprise D crew rescued him from the Jenolan, Scotty returned the chips and Starfleet finally got transwarp?