Yep, something like the first 4 to 6 months of 99K's might have been engraved by Enoch Tue - definitely some were before he unexpectedly passed away. But from 1928 to 1930's we see significant variations n the 99K engraving. We're not sure if Gough just wasn't as consistent as Enoch Tue (tho even there we see some variations), or if he maybe had other engravers working under him.
Here's a couple examples. SN 389,xxx on top, SN 309,xxx on bottom. Both Gough, but what a change.
https://i.imgur.com/U8Zgtf1h.png