Given all that you say about not having required information I think there is no way you can remove the lock yourself or get Apple to remove it for you (they will likely require the original receipt which it seems you do not have).
This support article has information about Activation Lock on your Apple Watch and how to turn it off as part of preparing a Watch for service or a new owner. --> About Activation Lock on your Apple Watch - Apple Support
- Apple can completely reset a device if a person can provide sufficient evidence of valid ownership. Do this online at: Activation Lock support request - https://al-support.apple.com/#/additional-support Apple says, "Proof of ownership documentation is required," but does not state what currently constitutes proof. Prior to this new online service Apple typically required the original receipt issued by an Apple Authorized dealer and documented provenance (so typically it would be the original owner who does this, or a descendant with legal proof of ownership). Apple recommends you keep your receipt after you buy an Apple device. --> Keep your receipt after you buy an Apple device - Apple Support