Hi,
without more information, best movement and case number, it's impossible to say something meaningfull.
As purely a guess and judging by what I can see only, it looks like made for the american market.
You may try to open the back, use your fingernails only - as you said, there is most likely a second cover (cuvette) which you can open as well.
In some cases it's not possible to open with the fingernails only - in that case you may ask a local watchmaker to help out.
In case you want to get some bettere founded information you can order an extract of the archives by PP through their website (but you'd need movement and case number for this as well and it will cost a bit).
Hope this helps
best regards
Suitbert