In addition to the three in our collection, we know of five other TR-48 computers. The first is located in Bletchley Park, England (the famous WWII code-breaking center). The Bletchley Park machine is cared for by John Blackburn, his son Chris and the other members of the Retro Beep Collector's Club. [As of about 2005 the Retro-Beep Club has become England's National Computer Museum and the collection is still in the same building.]
The second TR-48 is located in Padova, Italy at the Friends of the World Treasures Computer Museum which is operated under the auspices of UNESCO.
The third is part of the Digibarn collection in California. They have pictures of their machine...note the delivery truck with a lifting gate and the nice pnuematic truck they used to bring it into the barn. My nephew, 2 students, and I carried ours and almost ruined four backs!
[NOTE: As of 2024 the collection from Digibarn has been moved to the System Source collection near Baltimore. You can find their website here.]
A fourth TR-48 is located in the magnificent London Science Museum. Although it may not be on display. Don't worry they have plenty of other computing treasures to view up on the second floor.
A trip to lovely San Jose, California will let you see the fifth TR-48 in CHM. Don't miss this museum!