Grandpa John C. Witt probably didn't have a Texas Ranger badge issued to him. According to a Ranger history piece posted on the Texas Ranger Hall of Fame and Museum:
"When the Frontier Battalion and Special Force were formed in 1874, it was difficult for Texas Rangers to establish their authority. The State of Texas Adjutant General's Office began issuing Warrants of Authority -- impressive paper documents kept folded in their pockets -- to officers but not to enlisted men. This practice continued, in one form or another, until 1935 when badges and credentials were specified for all Texas Rangers."
But we do have his service record and pension papers that document his service in the Texas Ranger Frontier Battalion, Company D.
As far as the Frontier Battalion badges are concerned, that is best left to the experts at the Texas Ranger museum. You should read their write up at http://www.texasranger.org/artifacts/Fakebadges.htm before you jump out there and buy something that just isn't real or exist.
Letter from the Adjutant General of the State of Texas to the Comissioner of Pensions documenting the service of J.C. Witt in the Texas Rangers Frontier Battalion, Company D.