Good afternoon. Looking for some assistance on this bayonet.

1.) Is there any way to tell the general year it was manufactured? Or simply if it it WWI or WW II-era vintage? I read somewhere if one can read the ER or GR royal cypher mark, you can place prior to or after 1910. However,, I am not able to tell from the worn markings on this example. I am hesitant to remove the black finish over the marking to try to read it.











2.) what is the proper frog for the bayonet scabbard? Does it vary if it was WW I issue ir WW II issue? Is the sample photo below correct? if yes, for what era? nd what is the correct nomenclature for the frog pictured? And finally...is there a source for a suitable frog? A reproduction would be OK in this case.



Thanks in advance.