Need some information on TDC - 20 Speakers

I have in my possession two main speakers. They are quite large each speaker has two 10" woofers, two 4 1/2" mids, and two tweeters. The only label on them shows them to be manufactured in Massachusets and it states "TDC-20". In the research I've done I discovered they may be proto-type speakers from the late 70's or early 80's and they may have some link to the Tannoy company. Please help me identify and possible assign a value to them. Thank You.
Well I owned a pair of TDC speakers in the early 70s that were purchased at Tech Hifi. Tech Hifi was a New England audio chain store at that time. I thought the TDC name brand was the stores own because they were significantly cheaper than other more recognizable names. I don't remember the model number or driver configuration but at the time they were great sounding speakers for a high school student. Wow, I can't believe I remember all that. Been at this hobby a long time. I'll have to follow thisthread to see if anyone else has similar recollections.