F14 was super popular (#6 selling Williams game), so over the course of production, Williams used any parts of any color to keep the line moving.

Sneaky ebay sellers have even been known to replace lamp covers to all clear, and then claim the game is a prototype - even though the playfield has the much latter lamp boards.

The 10 prototypes have a X in the serial number, and the blue insert at the top says "Blue Plate Special" instead of the production playfield "Hot Streak" (above Yagov's head).

Supposedly the first 200 games off the line had PROTO ROMs

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