They are definitely not marine grade Stainless but they last well. They sell them every year and I bought some around 5 years ago. The tarnished one has held my PLB to the life jacket for that amount of time and its holding up will. The shiny one is marine grade bought in a chandler in Mallaig about the same time for comparison.
So saying I also bought the shackles to use on the car topbox..they still look like new but then..they are not in salt water. IMO Worth a punt if you need them..but don’t expect top quality stainless steel.