That tank looks like an older Fralo mfg. tank. Those tanks are in a minority around here. Most I find are distorted or out of round because they get backfilled empty. They need to be full of water before backfilled to keep their strength. I usually pump those in the dry part of year,if chance they might float. I have homeowner immediately run water to get them filled if in wet area or spring conditions at time of cleaning. plowking
Back in the day, like the 80s or early 90's i remember pink, blue, maybe a green etc. They also had colored facial tissue, but i knew it was bad for some reason, which is why they dont make it anymore.
Yes, you should call the plumber. He will be fascinated to hear that the lid came off, and there was sewage ready and waiting for the Turd Burglar. Make the call now!:laughing::laughing: