It might not mean DEAD, it could be an acronym...

Demolished External Architecture Design?
Design Engineering Another Day?

It would be easier to ask your consultant.

Yeah, i just figured it might be a "common" thing... thanks

I totally get what you mean - if your consultants are a decent sized, respectable outfit, then it's very hard to imagine filename suffixes slipping past modern office standards - unless the project's in the really early stages, when occasionally testing allows some lenience in naming protocols whilst things get established.

It's a tricky game to play, but we've found it really is in the interest of everyone to get a shared naming protocol agreed asap - which suits me just fine as I'm a keen advocate of hard & fast decision making so the "real" work can begin.

The best thing about your situation here is you get to approach the subject of being protocol gestapo through inquiry, and not nit-picking - ie.
You : "Mate, say, what's that there?"
Consultant : "er, o bollox, that's er, that shouldn't be there. Sorry. Good spot. I'll get that fixed"
You : "Ta"

...I'm sure you'll agree, that's a far better place to be than teaching someone the fundamental basics of egg sucking (ie. file naming) when links & xrefs need to be constant, and kept from daily maintenance.

Good luck chap.