Recently I bought a set of 8 memory modules that were advertised as “DEC VS4000”. They had a part number of 50-19464-02. This is one of the modules:
I had assumed this was for the VAXstation 4000 VLC, but it turned out not to be the case, the VLC takes modules that are physically narrower. However, they did fit physically in a VAXstation 4000 Model 60. Unfortunately they did not work in that machine and seemed to make the power supply think there was a short circuit.
On suggestion from the classiccmp mailing list, I dug out my DECstation 2100. I discovered mine had 10 of these exact modules installed, out of a possible 12. So now I know that this memory is for a DECstation 2100, and each module is 2MB. I tested the memory in the 2100 and it all worked fine. So now I can have 24MB in my 2100.