Yep, I figured out pretty soon after I posted that it was a #7 and not a #45. Do you know if the "ball" PV weight is original, seem they had a mix between ball and what is in the photo ad - which thank you for posting that ad / write up! It is very cool that he has what seems to be the 1st horizontal engine (assuming the model numbers are in order of release).
It is very interesting that Nate's is a steel tank and not brass. While there aren't very many examples of the #7, the ones I have seen are all brass tanks! When Nate's replacement ball weight comes in, he'll do a "walk around" video and with showing its original burner. Its a minor miracle the steel / tin tank wasn't rusted anymore than it was.
Oh and yours is the 3rd with a elbow for the steam line, so I think that settles that is factory. Perhaps denotes first runs out of the factory and Nate's steel tank even a earlier run?
EDIT: I just re-read that write up on the #7, "Early models were produced with Steel Boilers." So its going to be a 1890 engine!
Thanks
@txlabman / Charlie!
Here is a little longer run with Nate working the throttle :-)