I have a copy of Tombs & Treasure that has a sticker on the back of the cart that says "Sample." There is no other words on the sticker and it appears to be an official release of the game (the label has the right artwork and looks factory-made). Anyone have an idea as to what, if anything, the sticker refers to? (I'd post a pic but it's at my booth at the Seattle Retro Gaming Expo right now. I noticed it when I bought it, promptly forgot about it, then noticed it again at the convention.)

Open the cartridge and see if the board have EPROM.

Why would there be a normal front label (artwork and everything) if the cart was a proto or even pre-release? I've looked at what the normal "Sample" stickers look like, and this one doesn't look like them (even barring the fact that it has a normal release label on it, the Sample sticker doesn't have the name of the development company or say "Return to..." or anything like that on it). If you guys think this could be a proto or pre-release, then I'll take it off my table until we can figure out if it is or not. But just from the little looking around I've done on this, it doesn't seem like it is.

Here's my noobie assumption:

Random Game Store has a Kiosk, makeshift SNES testing station, etc. They need a game to use so they grab one off the shelf and slap a "SAMPLE" sticker on it.

Or it could be more official, who knows?

Probably was sent to a magazine or something to review the game before it came out officially.

I'm not too sure either, I think it could be something simple as a kiosk version of the game too. The more official to the retail it looks, it could be a retail version that's for display, the more proto-ish with eeprom-ish guts the innards look, then maybe it's a proto.

I can also go with what 3Gen said, usually a game could go out to magazine companies or strategy guide writers.

Yep, that's plausible as well.  I remember reading the Counselor's Corner in Nintendo Power as a kid and thinking, man, those guys have the best job in the world.