I was thrilled to speak with one of my oldest living great uncles, who confirmed for me that we are, in fact of the Ergueta bloodline that is related to the Spanish assayer, Antonio de Ergueta.
My great uncle saved me a trip, as he says his aunt researched the Ergueta line by going to Spain...
I think I have come to the right place. I chuckle, because my father and I have had an interest in coins and stamps (his is much more than mine), and he has never told me the story of how the first "Erguetas" came to Bolivia until today. I have been trying to uncover the branches of the family...