The Type 512 oscilloscope was introduced in 1949 and was in production 6 years. The 512 added some features specifically missing from the 511, specifically increasing the vertical gain and DC coupling to improve the lower bandwidth. The upper bandwidth, however, was reduced from 10 MHz to 2 MHz.
This ad for the 512 appeared in the March 1950 Northwest Electronics World magazine (really a 12 page flyer).
These two photos are from a Tektronix Photo Album, date unknown.
We have a Type 512 oscilloscope on display at the museum.