Why some rings are marked and other is unmarked?
This is easy question. - It's always all about money.
Same thing today, same was before war. If I want to sell officially in store I have to follow rules - I have to hallmark in Proves Valde. There I have to pay for checking silver content, for hallmarking itself and biggest part is tax on silver.
But when somebody comes direct to any workshop and orders something they do get asked how important is official hallmark. And since there is difference in price in most cases customer chooses not to have officially hallmarked item. Sure sometimes he still wants some hallmark, anything - then he can get meaningless 925 informative stamp or old German stamp, whatever.
