"It is listed as MODEL TCP-MON Series H*o8*81. "
Based upon the above, plus the addition
of "Bogen" or "Tech Craft", I came up with
goose-eggs on a search for a manual.
I did manage to score this manual,
for a 35A:
https://www.bogen.com/products/pdfs/...dfs/PI35Am.pdf
Is that roughly what yours looks like?