This is is great price for two stainless steel plates and engraving pen, but I am interested to see how durable would engraving hold compared to all other stainless steal plates.
I would support suggestion from SFR10 and you should really send your plates to Jameson Lopp who is testing them all the time.
My favorite backup solution is stainless steal washers that are cheap and durable, but I think AirGap Recovery Plate can easily compete with competition.