1956 Pacific Great Eastern Airchime MK5H "Mr. K"
This 1956 sandcast MK5H is from Pacific Great Eastern railroad Budd car BC-33. This horn is one of only a handful of Modification-K horns in existence today. The Modification-K back cap was a way for Airchime to attempt to let users set speaking pressures for K horns. These caps predated the more common adjustable cap by about 10 years.
The MK style cap was only offered on horns with serial numbers between 3232 and 3566 per an Airchime parts list.
This specific MK5H was delivered in a batch of horns on July 23, 1956.