Hi, Bob!

Welcome to the Forum.

Sorry, but TBD doesn't mean anything.

S&W went from a single letter serial number prefix to a three letter prefix to allow themselves more flexibility and variety in numbering.

In some special order circumstances, S&W would assign a "custom" three letter prefix (such as CHP).

"TBD" simply came after "TBC" and before "TBE", and had no more meaning than that.

I have prefixes of "AJL", "TBL", "AYM", "TBH", "TED", TEV", "TFF", etc.

They all mean nothing.

John