It's probably so expensive because it is one of the first ever made. I happen have one of the first 1391401's. Mine is made on 12 Mar 1987. So my keyboard was made before they released the IBM personal System 2 on 2, April 1987.If anyone has an earlier 1391401 , I wanna know. Well with this keyboard on ebay, I can clearly say that from November 1985 onwards , IBM AT's were bundled with the Model M rather than the F AT.