On an visit to the RAF Oulton museum today I saw, in a framed display case, the above object. They were stored in tiny cardboard boxes only a few inches square and very narrow in depth. Inside was a small parachute that supported a spool of 'window'. Apparently, as the spool unwound the strips would disperse into a cloud of foil. I have never heard of this method of delivery before and neither of the two volunteer museum guides could tell me anything about it. The spools were no wider than the tapes found in old music cassettes (for those of us old enough to remember them) and nowhere near the dimensions of the usual strips of window. Can anyone shed any light on these?