The easily recognized Yellow NES Test Cartridges were used by Authorized Nintendo Repair Centers to easily test various functions of the systems (Control Deck, Power Pad, Joystick, etc). In addition to specialized cartridges for testing, there were also two carts, which are just the regular versions of the game, only in a different colored casing.
One of these is the Yellow Zelda Test Cartridge, which happens to be up for sale at the moment.
I know of two of these off hand that have sold for $600 or so in the past couple of years so the BIN on this guy is not insane, but probably a bit overpriced. Even at that it’s quite a bit better than the one that was being listed for $1299.99 several months ago.