What is Zenith Plate

[wiggy131]

Need help with this Spoon from the Isle of Man - what is Zennith Plate A1 and what date would it be around?
Thanks for looking! One of my images refuses to upload! It says Zenith Plate EPNS and A1
Thank you!

[AG2012]

Hi,
The only source I have is here:
http://www.925-1000.com/silverplate_Z.html

EPNS stands for electro plated nickel silver.
A1 indicates the highest quality of silver plating, seen on British silver plate.
Regards