Want to replace with a standard coupling
What does it look like is it a American locomotive?
After looking at Hoseeker it appears Atlas has many different couplings, we need the model of your locomotive and approximate age.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951

My Model Railroad
http://melvineperry.blogspot.com/
Bakersfield, California
Aging is not for wimps.
Hello All,
What is a “standard coupling”?
If you are referring to a knuckle coupler then see the Kadee website.
Look under the “Coupler Conversions” tab.
Hope this helps.
You model N scale I believe.
http://www.irwinsjournal.com/a1g/a1glocos/
When Atlas began supplying that scale they bought on from Rivarossi in Italy.
If that link doesn’t help try Kadee/micro trains
https://www.micro-trains.com/conversions
Is it one of your C Liners?
Fixed it. N scale forum helped.