About Longines Cal 9.47N

Hi OF!

Recently I came across with this Longines Art Deco Tank with Cal 9.47N that resembles the Einstein's Tonneau Longines. I am a vintage dress watch geek and really have a soft spot for that. Some details:

Case: 14K gold filled Wadsworth, probably cased in US. Correctly me if I am wrong. Both sides have guilloché engravings. Believed to have enamels but eventually lost as it ages. Observed a significant scratch on the left side of the case.
Movement: Cal 9.47N with 17J. Recently serviced in 2019 with new mainspring
Dimension: Width 22m without crown. Lug to lug 38mm. I think it has quite a wrist presence for a tank watch
Accessories: Come with a original watchbox claimed by the seller. I personally think it's not the original one, but a period matched.
Serial number: Watch dated back in 1925 which is 95 years old now. I am impressed by the condition considering the age
Asking price: USD1000

Some questions:
1) Is the price reasonable? I came across some similar design sold for sub USD700 back in few years ago. However I rarely seen such top condition for a similar design at this age. Please let me know is that justified.

2) Could anyone shared with me some info regarding Cal 9.47N? From Googling, people seems to associate them with Cal 20.28. Is this movement reliable and hard to source for parts in case of servicing? I believe it's not commonly used

3) What does Longines 10 grand prix means? Something associated with Longines pocket watch isnt it? Hence I don't think the box is originally come with the watch.

Feel free to drop your valuable comment & advices.

Thanks and have fun!

Price is high, however this is quite a nice example, in good condition for its age (~95 years old). Caliber 9.47N is a very high-quality movement that appeared in quite a few rectangular Longines from the 1920s. This is an American market example with an indelible, radium dial. The Grand Prizes, noted on the box, refer to international competitions that Longines won. I do not know if the box is correct for the era but it does not look entirely dissonant.

I wouldn't expect this case to have enamel. Is this your assertion, or the seller's?

Nice watch. Longines recieved their last Grand Prize in Barcelona 1929
so the box is probably later.

It was stated in the seller's description. I too have some doubt.

Found a similar design from a japanese blog:
https://shop.plaza.rakuten.co.jp/sweetroad/diary/detail/201601060000

I think quite possible box came with it.. many things were made and not delivered and/or sold for many years..I have multiple pieces with manufacture and sales dates running 3-5 years apart.. albeit I must say most are in the 30's. Often pieces went into stores and sat there for a very long time before being sold. You could buy 20 year old new Rolexes in any middle eastern shops not so long ago and just because made does not mean sold.

I really like the overall design, the dial and the movement and the box looks great -- but the price seems really high when you consider the loss of plating around the bezel.
While they say a watch is worth what you’re willing to pay for it, I would not want to pay much more than half the asking price, I'd say 650 dollars should be the absolute max IMHO and even then I find it expensive.
I'd say you're not guaranteed to resell it at that price should you some day tire of it or need to resell it.