Anybody know what this secret agent microcassette player is?

The label makes it look too professional to be a film prop. Any idea what the connections are ? My guess would be a Military circular connector (which cost about £50 each). If so that would give you a good idea of the type of customer. I would also guess that it was actually the 91st unit made rather than the 30091st.

Actually the look and construction reminds me of some antenna test sets a friend bought and found at a amateur radio rally paying about £100 each for five of them. He only managed to sell two of them - for £3000 each ! Being an aircraft techinician he knew that test set was required equipment for doing maintenance checks on a particular type of airliner.