Very interesting. A TL-15 is an excellent container, but I'm not familiar with a 5 wheel combination lock in commercial service in the US. I have a S&G vault lock which has 4 wheels. I don't doubt 5 wheel locks exist though, especially if the safe was possibly installed for a US Senator. Would definitely be interesting to see some photos of the lock (both outside and inside) if you still have any.
Reminds me of this: https://blackbag.toool.nl/?p=31