The most apparent changes showed up on the 1947 Postwar or Modern version of the K-4 and included a solid drop-coupler pilot

This is the one that started it all for us and for all the laser cut companies for that matter

This is a McKean Models 1510 HO 4-Bay ACF Covered Hopper W

This Kit Measures: 2-1/2 x 1-1/8 x 2

They also have adjustable buffers

B.T.S. 7701 S #112 2nd Street House - Kit (Laser-Cut Wood) ProductID_11467342 The most apparent changes showedThis is a B. T. S. 7701 S Scale #112 2nd Street House Kit (Laser Cut Wood) Footprint: 17 x 34' 5. 2 x 10. 4m Condition: Factory New (C 9) Operational Status: Functional Original Box: Yes (P 9) Manufacturer: B. T. S. Model Number: 7701 Scale Era: S Modern Model Type: Building Kits The Trainz SKU for this item is P11957155. Trainz Product Id: 11957155