I just picked up a copy of "The perfect portable - Featherweight 221" by Nancy Johnson-srebro and according to her souces the keys to type two and type three carrying cases IS interchangeable. If you have a british case, then it will not work. The type two has a lift out tray the type three has no lift out tray. If you are like me you might not think the above mentioned book would be worth the cost (slightly over $20.00 Cdn.) but it has given me alot of history I wouldn't otherwise have thought about and also has a short section on trouble shooting which is also handy. If you don't have a manual for your machine they have reproduced some of it in the last section. I personally own a K222 and it has extra information on mine as well. It is worth the price for the interesting history alone -- IMO only. Budster