As this is one of my sweetspots I have interrupt. Yes, sorry guys, but it's out there; I have to react
You can say many things about the frock, but it is certainly not borrowed from a Navy sweater. Yes it's wool, yes, it's ecru.
That's where any comparison stops!
It's longer, thighter, very different construction, no roll neck and I'd venture to say it was thicker.
An RAF frock is nothing like a Navy sweater.
Ask Chris, Dan or better Richard; he owns a couple of frocks!