It is the #178.
The Kadee Magnematic is the coupler of choice in HO. All metal, very strong, couples for just banging two cars together, will uncouple automatically with a magnetic ramp set between the rails. Looks like a real coupler. Assuming you have equalized coupler heights between all your cars, it stays coupled. Cost is about $2 a pair, and last time I visited my not so local hobby shop, the competitors were about the same. In other words it doesn’t cost much, if any, more to buy Kadee’s, so why not buy the best?
Kadee’s came on the market better than 50 years ago and have been a steady favorite. The Kadee patents finally expired in the '90s and other makers (McHenry for one) started selling clone couplers. Clones look like Kadee’s, intermate with Kadee’s, and are mostly molded in virgin plastic. Many of them have the knuckle closing spring molded in one piece with the coupler itself. These molded plastic finger springs are subject to breakage or taking a set. Kadee’s and the better clones have a tiny bronze coil spring to close the knuckle which is far superior.
I buy and spiff up a fair number of el cheapo train show cars. If the car has working knuckle couplers I leave them on. When they break I replace th
KD’s are the best way to go from the start. Highly recommended. I’ve also replaced many RTR with other couplers with KD’s always the right move. KD is the defacto standard period. On the others you get what you pay for.
PW