age origin and makers name on inside case of a watch dating to aprox 1920

Hi I took a gamble on a gold watch at auction and I am trying to identify the hall marks

top row in a diamond lozenge a 9 on its side then .375 followed by a triangle in a lozenge and then a D in a lozenge. I understand this to be ( ct but what date and assay?

Below this is S A in seperate lozenges


and then below that is what looks like a hammer with ISO or 150 within it, I believe this is the makers name but I cannot find any trace

Below that is a serial number of 43244

any help would be appreciated thanks

Stuart