For my story I need a data storage device that will be reasonably familiar to adult readers. My character will have obtained this device and know that vital information is stored on it, but not necessarily in what form. It needs to be obsolete so can't just be plugged into any handy laptop or PC, in fact it should be a real hassle to access the data. My initial thought is a 3.5 inch floppy disc but I'm not sure if this is difficult enough to get data off.
As well as the actual storage devise you can also consider factors such as out of date software etc that would be needed and therefore add to the difficulty of opening the data.
My character is highly educated but completely unfamiliar with 21st Century Earth technology, but can access the internet to look things up but will want to avoid anything that may facilitate others tracing them. They have access to cash but not banking/electronic money so e.g would not be able to order anything from the internet or pay for any services online.