Help identifying "SI" hallmark please

Looking for identification of this hallmark. The pendant and ring were owned by a relative who lived near Winslow, Arizona. Appears to be “SI” with an arrow, but a google image search didn’t turn up anything. Thank you in advance!

checked all the usual places with zero hits on these marks

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Thanks Steve…I’ve not had any luck, anywhere. All the other pieces that came in the collection were from notable artists and of good quality, so these have me stumped!