Thank you all for responding. It turns out I am looking for a #671-186x collector insulation board and it only fits a 1946 Lionel 2020 and 671 engines. The slot for the collector terminal is on one side at the edge on this part, not centered as on the 671-186 that is for the 1947 and newer engine. Send me a message if any body has one for sale. Dave W.