Somebody is pulling someone's leg. I have a Turnbull Pietta (Great Western Custom II) with TruIvory grips. If you saw it lying on a table, you'd swear it was a USFA. I bought it online about a year ago for $500.
Mayhaps ! but it's gone..sold to somebody or someone..no idea the selling price, but if it was the asking price, somebody or someone made PT Barnum a sage !
BTW how is your gun marked ? The one I saw was not Great Western marked.
The one I saw had the FAP Diamond & a Turnbull prancing Bull stamp and had very nice one piece walnut grips.