I see that the article states it's 1:24 but I suspect that is incorrect. I was in G scale from about 2002 to 2016 and 1:24 was no longer made by then. The article is dated in October, 2019 and introduces the PIKO locomotive. In the OP he didn't identify it as a Reading locomotive. Since it's a Reading loco and it would have run on standard gauge, I believe the model would be 1:29.
Yea. Apparently the Reading had several different types of the 0-6-0 Camelbacks too. So you’d have to know what type it was and compare the length of the prototype to the length of the model.
May be easier for OP to just ask Piko, although it would be an interesting research project. I saw also that they used different tenders, as a lot of steamers did depending on how the loco was used.
It was posted earlier that the model is 20.3" long. If my math is correct, In 1:29 the prototype would be a little over 49 feet, in 1:24 it's a little over 40'. I could not find where the Reading camelback length is listed.