Very Large Silver Concho Hallmark

I purchase six large story teller conchos for my wife last year and want to now place them into a case for display. Until two days ago I believed they were unmarked when I removed on of the leather backings from one and to my surprise it had a hallmark. Hallmark picture is attached with one pic of one concho. I have always been able to track down hallmarks but not this time. I have turned to this site for help. I thank you for any info you may offer.