Yep, that is on old brake controller unit. I would not reuse it. You can get a nice electric break controller from Tekonsha (I have the Prodigy) that has proportional brake signal and is very adjustable. I assume your trailer has electric brakes.

68 Road Runner (383/4speed, post car w/decor pkg) - Major Project
69 Road Runner w/472 Hemi & 4 speed.
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2023 Ford Mach 1