Mike you definitely got a bargain. I just snagged a nice 500 from EBay. It should work well with my PM Research #3. I’m regretting selling most of my stuff a few years back. I had 2 of the 504s and a nice SH4 return flue boiler. Those appear to be extremely rare. If I recall correctly it was being sold by a pawn shop. It was brand new with a water pump and tank. It had a $500 buy it now and I jumped on it. That was one advantage of starting my job at 3AM. I would check out eBay while I had my coffee and a cigarette before getting ready for work. I got some good deals on new listings.