Gold Ring - Victorian?

Hi all, could you kindly help me with a dating of this ring. I read it as 18ct, Sheffield and P (1864?). Kind regards, Adam

 

Apologies, I wasn't able to add the below images in the post. I have also added the maker, in case it rings a bell.

 

Where?

 

Ah, there

 

Yup

 

https://www.loveantiques.com/items/...ngham-1911-half-hoop-five-stone-ring-LA534414
Same mark on this ring, but no info on who's mark it is

 

Birmingham.

 

The crown is the Gold Standard Mark (comparable to the lion passant for silver)
https://www.antique-jewelry-investor.com/crown-hallmark-comments.html
"When people see a crown mark they usually identify a Crown as the Gold Standard Mark. This was first introduced in 1798 and can now been seen on All UK hallmarked gold that's 9, 14 18 and 22ct. The crown also appears on old estate and 15 carat gold jewelry, however this was stopped in 1932.
However, there are quite a few crown marks, for instance the city mark for sheffield in the UK is a crown mark within a shield."

 

I wasn't able to find any other info on what the differences are, but could it be that the town mark would never be placed before the carat no.?

 

https://www.marmaladejewellery.co.uk/advice/hallmarks-a-guide/#page/10
"In 1773 and partly due to the efforts of Matthew Boulton, a renowned silversmith, Birmingham and independently Sheffield got their own assay offices to mark silver only; respectively using the Anchor and the Crown as their marks. Birmingham started hallmarking gold in 1824 and Sheffield in 1904. Due to the mark of 18ct gold being made a crown in 1798, when Sheffield started marking gold in 1904, they needed to change their Assay Office mark so as to avoid confusion. They changed their mark from a crown to a York rose for items of gold."