Do think these are related?

Look the same other than the mono and size

 

I agree, looks the same, but the opposing swirls at the bottom of the design are slightly different.
There are also frilly bits at the sides of the smaller ones.

 

Both groups are in the Kings pattern, which pre-dated the custom of patenting a design. Lots of makers, some with slight variations, and over a very long period of time.

 

1857 Austria Hungary
and some bloke in Sheffield

 

D&A should be Daniel and Arter of Birmingham.

https://www.925-1000.com/silverplate_D.html