Here are some pictures of the cord I mentioned a while back, the
cord that fed the two receptacles in the optional installed part of a
1973 trailer. The cord cap is marked GE, and I believe the cord is
SJ-something, but I couldn't read it, and the insulation is rubber.
This cord was just lying on the ground in the crawlspace. I snapped
the cord off where it goes through the floor, took these photos, and
threw it on the scrap pile. This was plugged into a matching Hubbell
30A 240V recept, which WAS wired to a two-pole 30 AMP breaker, just
turned off. It, and it's cable leading up to the panel, were removed
when we replaced the panel. The outlet is still there, we're just
trying to find an outdoor blank plate. I need to get pictures of the
outlet, tin snipped hole the cord went through, and how it was back
stabbed into a equally-old receptacle. In case you're wondering, those
outlets are disabled, and are waiting for blank plates.