1981 ProCo Rat "Big Box" — LM308N, CTS pots, original Kalamazoo build

Serial RT-012930. One of the earliest production Rats built by ProCo in Kalamazoo, Michigan, before the pedal became the industry standard it is today.

This is the version everyone chases — and for good reason:

• LM308N op-amp — the National Semiconductor part that gives the early Rat its distinctive compressed, singing sustain. Later revisions moved to the OP07 and eventually the current LM308 in a different package; none sound quite the same as the original 308N. Verified visually on the board.
• CTS pots dated 1378118 — CTS source code 137, week 18 of 1981. All three pots are date-consistent, so this pedal was assembled in mid-to-late 1981.
• Original enclosure — the tall "big box" format Rat only used for a few years before ProCo switched to the smaller pedalboard-friendly enclosure. Honest wear consistent with a working pedal that's been played, not a safe-queen.
• Made in USA — Kalamazoo, Michigan address on the rear panel. Not a reissue, not a Taiwan-era part.
• All original internals — no modifications, no re-caps, no changed jacks or pots. Board and wiring exactly as it left the factory 45 years ago.

Controls: Distortion, Tone (Rat's famously dark low-pass), Volume. 1/4" input and output, 9VDC battery eliminator jack.

Powers on and passes signal on 9V battery (not included). Distortion sweep is full and even from a light overdrive at 8 o'clock to full Rat snarl at 5 o'clock. Tone control is smooth across the full range. Volume knob has clean taper. Footswitch clicks positively; no bypass issues.

Cosmetically the enclosure shows honest use — scuffs, minor paint wear at the edges, and light scratches on the top panel. Nothing that affects operation. Original graphics still crisp. Rear panel Velcro is aftermarket from a previous owner's pedalboard. The original feet are on the bottom plate...turned inward. Easy to reverse if you want feet.

This original-owner pedal has done what it was built to do: forty-plus years of live gigs, studio takes, and bedroom sessions. It sounds like a Rat should sound — thick, cutting, and unmistakable.