What is this mysterious part? The internet has whispered it to me, and I will pass this information on to you. This is a replacement battery door for an HP 11-C Scientific Calculator, a wonderful machine which was manufactured from 1981 to 1989. Its unusual form factor, delicious keys, and deeply consistent use of RPN won many hearts, and its incredible durability have kept thousands of units going to this day. Mine is 35 years old and they will, in all seriousness, pry it from my cold dead hands. The only thing wrong with it is that sometimes the battery doors get lost. This part fixes that. @gmgerken
Thanks! It works great. Maybe put some tags and a description on it? I can't be the only one.