We have discussed “Stainless” on several occasions … But this one was new to me

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A box of teaspoons with a note on the inside of the lid, stating that they were a Wedding Present in June 1941
There are only four, but they are in immaculate condition after 80 years !
Does anyone recognise the brand, or know the metallurgical composition ?
… They do appear to be non-magnetic.
MichaelG.