Using this from TH https://www.trumpetherald.com/forum/viewtopic.php?p=1367115 and a search on eBay, I'd guess MasterWannabe's 2055T is possibly a 1986-1987 model if it says Eastlake above the serial number, which would be perpendicular to the valve casing, but more likely an early 2000 or later, especially if the serial number is parallel to the casing. There's a claimed 2001 Silver Flair listed with serial number 85XXXX. A trumpet with a serial number starting with a 3 would almost have to have been manufactured in 2000.
Once again, using the information from TH, Richard III's euphonium appears to be simpler to decipher. 1995-2000 would be my guess, thinking that a letter prefix was used and thinking that an A could have been used for euphoniums instead of the S said to have been used for trumpets at the time.
I welcome corrections from those more knowledgeable on the subject.