Need help please to translate from Japanese writing on 1940's fountain pen nib

[brad carlson]

I would appreciate if anyone can translate into English what is inscribed in Japanese on this 1940's era fountain pen nib.
Additionally, does anyone know why there would be both English and Japanese on the same fountain pen nib and the name of the manufacture? The nib is inscribed with Y.S. Co. but I could not find a company with those initials that would have made something like this in the 1940's.
Thank you for your time!
BC

 

[SomeCallMeChris]

保證 (ほうしょう・houshou) is an alternative form of 保証, meaning 'guarantee' or 'warranty'.

There's a good chance that this is actually Chinese writing, but I don't know if it means the same thing in Chinese.

 

[brad carlson]

great!, thank you for the feedback.
BC

 

[Toritoribe]

證 is the traditional form of 証, so it could an old Japanese one.

 

[Uncle Frank]