Rogi
1407
It can be either or.
My initial observation was that the double serials were early models of HF or an early Observatory Chronometer as most of these pieces have the "electric" logo beneath them, but there is no consistency to the method, I've seen both ways of serial (one and two serials) on both older and "younger" movements, this could indicate a transition period between the years.
The movement could have had a service, had parts replaced etc. or just come out after a certain year or within a certain batch. Without further evidence we can only show our own observations on this phenomenon, it'll be interesting research for the future 
I'll share some of my observations in an upcoming thread
I like the piece you posted a lot, especially the patina on it 
shows it has had a life enjoyed and worn by its owner. Have you checked this HF's numbers with GP?
Another GP HF Chronometer
Very cool find!
yeah, I was wondering too...
I'm already in contact with Willy at GP Museum about my Observatory.
Hang on a second.
Interesting indeed
It can be either or.
Looking forward to read your observations.