In April two Vintage 1977 IBM Model 5100's were listed on ebay one working and one not. The working unit sold for well over three thousand dollars and the broken one went for close to a thousand dollars.
Timothy Fagan of Winston Salem, NC. (the seller) was kind enough to let me use his listing info and photos.
You are bidding on a vintage, working, IBM model 5100 'Portable' Computer. (Portable??? At 50 lbs, I wouldn't want to be 'porting' it too far...).
This model was introduced by IBM in 1975, and was on the market until 1978. There is a label inside this machine with a 1977 date on it. When they were originally sold, they went for $9K (16K ram, BASIC language only), to $20K (64K, BASIC and APL languages). I don't know how much memory this machine has, but it does have both BASIC and APL (the BASIC only models did not include the BASIC/APL toggle switch on their faceplates). This machine very well could've cost $20,000 less than 30 years ago!!! This model was sold with a datatape cartridge which held programs the user could run to accomplish what they needed. Unfortunately, I don't have a cartridge for it. I do however have a 5100 that works (also without the tape), and it boots to an OS (must be in ROM), and you can type commands at the prompt.