That's great info Marty!
Here's an example of a '67 pump, note that the "0" is lightly stamped.
054th day of 7 with a Tonawanda stamp of T0330

A few more.

Pic 1 is 68 or [R] type. [valve]
Pic 2 is 69- or [S] type [no valve]
Pic 3 is marking on pump in pic 1. 10th day of 73 so a replacement??? It is NOS
Pic 4 is marking on pump in pic 2 157th day of 69


Pic 5 is 77th day of 69 and is [S] type but marked [U]???
Pic 6 is 105th day of 72 and is [S] type but marked [W]????

Have read posted info before but these odd, marked ones are not rare at all. That is why I have always thought the [1S] was 69- up Chev.

Always looking to learn.

Are we anal, or what? :haha: Back in the day, the only thing we cared about smog pumps was how quickly we could remove them and throw them in the dumpster.

Guys i have a used smog pump, 7801149 but i have no stamped date code i can find. I read GM may have eliminated the date codes after the 69 models. I looked at all the flat machined surfaces and wire brush with a good rust oil and still no codes anywhere. It has the black fan and it looks like a original GM pump. Any ideas?

Well, as evidenced by many of the examples in this thread, GM did not eliminate the date codes after the 69 models. Could be a warranty replacement or just didn't get stamped.

Take the black fan off they have a date molded into it

Thanks i will try that.

That is what i thought too. Warranty replacement or never got stamped.