[Hallicrafters] S-40A Tube type change?

[rbottomleysr at dslextreme.com]

I have an S-40A with a type 80 tube in it. Does anyone know when the
rectifier in the S-40A was changed to a 5Y3?
Back in about 1958 I wrote to Halli and asked for a service manual and
they sent me an Installation and Operating manual dated October 1949, form
94x519, and a Service Bulletin for Model S-40A dated Jan. 1950, form
94x385, run No. 3. Both these documents show the rectifier type as 5Y3GT.
Any help out there on change dates?