Looking at the files in the recent UK MoD release, I noticed that the drawing of the "rhomboid" craft observed over Ardingly W.Sussex UK on 4-Sep-1989 (file: defe-24-1938.pdf page 167)
(which indeed is somewhat similar to a US F-117, but a F-117 has wings whereas the report stated "all solid body, no wings as such"), is quite similar with a UFO observed over Port Washington WI USA in 1998 as presented at the NIDSCI website (see drawings at end of page)
http://www.nidsci.org/news/wisconsin_sighting.php
Note: the latter exhibited unconventional characteristics.
(which indeed is somewhat similar to a US F-117, but a F-117 has wings whereas the report stated "all solid body, no wings as such"), is quite similar with a UFO observed over Port Washington WI USA in 1998 as presented at the NIDSCI website (see drawings at end of page)
http://www.nidsci.org/news/wisconsin_sighting.php
Note: the latter exhibited unconventional characteristics.