Authenticity of big pilot 5004-01

Hi there, I'm thinking of getting a pre-owned big pilot 5004-01 from a store (not AD but it has been around for 50 years). The watch was originally purchased in 2012, comes with complete set of box, manual book and warranty card and it's in mint condition. My only concern is, at the back of the case, there's a 7 digit serial number (380XXXX). This is rather unusual? Can anyone advise on the authenticity of this watch.

p/s: The watch seller also provide a 12 month warranty and provide Buy-back Guarantee of only -15% depreciation or trade-in for -10% depreciation.

Hi, Jinster!
Welcome to the forum!
The BP 500401 is a great watch. And there is nothing wrong with the serial number. IMHO I think a seller would not give a 12 month warranty if there´s something wrong …
Best,
-c

Agree with comments re guarantee plus a shop of 50 years standing is not
going to ruin its reputation by selling fakes.

Thank you guys. Maybe I'm being overly concerned. Can you guys tell me more about the serial number at the back of the case? I've seen quite a few BP500401 on the internet and none of them have a serial number at the back of the case. Is there a particular reason why most BP500401 does not have a serial number at the back of the case but the one I'm looking at has it?

The serial number may have been blanked out using photoshop, to prevent fakers copying?

I just checked mine and it has the serial number on the back between two of the indent holes.

cheers guys!

there should ALWAYS be a serial number on the case back.

good luck,
thang