AR mods are solid devices. 250 for an authentic sounds about right if bought at a B&M Back then. It is a standard 510 with a 2 piece adjustable pin. In the future, to remove the atty, loosen the 510 pin a bit and it should come off easily. I am not sure it would have helped with that one with how rusted on it was. A modern single coil 22mm atty would be real nice on that RDA or RTA, your choice. Most kicks are 15mm in height which means you would have to use 18500 batteries in it so it will all fit. If you study up and are careful to check your builds, you should be fine using authentic 18650s without a kick. That mod is not a hybrid and is one of the safer of the old mech tubes. I would disassemble and clean and inspect every part of it including the button assembly before using it. You want to make sure everything is in good working order.