PDP-11/20 vd one that just says pdp 11 what are the date differences?? OEM?

[Christian Corti]

On Mon, 22 Feb 2016, Paul Birkel wrote:
> My PDP-11 is labeled as "S-386" and dated 9/23/70, which I guess makes it
> fairly early in the production run (but I do wonder what the initial
> manufacturing rate was given the relative riskiness of this new
> architecture).  Anyone have S# and dates for "plain 11" vs. 11/20-marked for
> comparison?

Our PDP-11 is labeled as "S-308", the date is 9/16/70. And I think they 
called it PDP11-20 from the beginning, as the model number above the 
serial number says "M11-20"

Christian