Introduced in 1986 as IBM's first true "Laptop" type computer, although since it weighed almost 12lbs, it certainly wasn't something you would want to operate on your lap. But for 1986, it was a technological breakthrough and offered the ability to run without the need to find a power outlet. I am sure that IBM was not the first to introduce a portable like this, but for a portable it was very powerful at the time. The machine was powered by a low-power 8088 processor, designed to stretch the battery time to it's maximum.
A well equipped machine and it would have to be to sell a computer with an older processor in it and no hard drive. These were probably left out for 2 reasons: 1) the cost of putting them into a smaller case would have made them too expensive to sell and 2) the battery probably would have lasted 10 minutes. It originally sold for $3500 which was not bad considering that the AT and XT/286 models sold for almost twice that around the same time.
This is another machine I know very little about, but I know I wouldn't pass one up at a flea market since I like fiddling around with old computers. It is not easily upgradeable because it does not have expansion slots, but an optional printer can be attached to the back giving a very clean appearance. Space saving ideas included using 3.5" drives to save space and removing the expansion slots to allow the board to fit into its small shell.
If you are looking for files for your PC Convertible, goto this site and click on PC Convertible downloads, there is one file listed there which may or may not be useful to you.
Another excellent link is this page which has more extensive information on the PC Convertible and a few more downloads than given above. I think if you take a look at it, you will not be disappointed if you own one of these machines!