Antique early 20th century boxed set of six fish knives and forks in original box probably shagreen truly stunning the quality and craftsmanship is outstanding  handles are probably bakelite the blade is marked firth staybrite with beautiful engraving to ends velvet interior 23 cm wide 18 cm width 6 cm tall some age related wear to box I don't think the cutlery has ever been used 
Firth Staybrite is the trade name for a stainless steel alloy developed by Thomas Firth of Sheffield in 1924. The alloy is made of 18% chromium and 8% nickel, and is also known as 18/8 stainless steel. 
Discovery of stainless steel 
Harry Brearley discovered stainless steel in 1913 while working at the Brown-Firth Research Laboratories in Sheffield
Dr. W. H. Hatfield developed the 18/8 stainless steel alloy in 1924
Use of Staybrite 
Staybrite was used in cutlery, kitchen equipment, and kitchen utensils
Staybrite was also used in watches and jewelry
History of Staybrite at Old Hall
Old Hall began producing tableware in 1928 using Staybrite 
Pre-war Old Hall items were marked "Staybrite" or "Olde Hall Staybrite" 
After the war, Old Hall changed the marking to "Stainless Steel" 
History of Staybrite at Firth Brown
Firth Brown sponsored a large area at the 1934 "Daily Mail" Ideal Home Exhibition called "Staybrite City" 
Firth Brown continued to develop new uses for Staybrite products 
Shagreen is a type of leather with a pebbly texture and raised pattern. It's made from the rough, untanned skin of various aquatic animals, such as sharks, rays, or stingrays. Shagreen is often dyed green. 
How it's made: 
Shagreen is made from the rough, untanned skin of aquatic animals.
The skin is covered with small, close-set tubercles.
The skin is then dyed, usually green.
What it's used for: 
Shagreen is used to make furniture, boxes, and cigarette cases.
It's considered a luxurious material, especially when paired with polished chrome or brushed brass.
Man-made replicas:
Man-made replicas of shagreen are widely used. 
Faux shagreen is available in a variety of colors, including eggshell, linen, oatmeal, and more.