A Ranchero 2996-4? An 18 million serial number (cal.285) 1961 Ranchero??

Hello all and thank you in advance. Been poking around on the past threads for help on this one. It’s and Ranchero 2996, cal. 285 with a 181XXXXX serial. Is that possible? I’ve seen some military Seamasters with ranchero style dial dates to the early 60’s. This one does have an engraving, but I think it’s personal. Just would like to know if this movement was swapped in at some point? Everything else looks legit. Unfortunately no Extract included.

p.s. I’m sure some of you have seen this one, it’s from the UK.