Here is a picture (the top was removed prior to taking the pic) of what mine looked like before restoration. From what I can find online, the Wayne 70's with high mounted sight glasses are much less common than those with the low mounted sight glass. Of the high mounted sight glass pumps, most have an ad glass between the sight glass and face, so my pump is a fairly uncommon version. I'm confident that my pump was manufactured with no ad glass because I media blasted the doors myself. There was no evidence that there was ever a hole where the ad glass would have been.
I agree that pumps without ad glass were often purchased for commercial applications. From my research I did learn that some brands did not use ad glass, so maybe an independent station owner ordered the pump without the ad glass knowing that his brand didn't use ad glass. I've seen pictures of brands that didn't use ad glass and simply had the ad glass painted over.
Lastly, There is a member here who has a 70 with the low mounted sight glass with NO ad glass and an original nameplate that says "70".