Wolf Press, AZ, did a book on Rocky Gibbs. What I remember, briefly, he was in Denver, there was a gun club with a competition. Least drop at 500 yards (?). He reamed out a .270 WCF to what became Gibbs, blew the shoulder forward. I think he insisted on a 1 caliber neck length. And with that pot of powder, he won consistently. Demand made him a gunsmith. He was very careful in making his chambers. Liked Denver '43 surplus /'06 brass. Stronger, he felt. Not unlike Mr. Ackley, sharp shoulder, blew it as far forward as feasible and used the powder capacity in common rifles. 98. Springfield, etc. Calibers from 6mm to .338... So what you are looking at is a hot version of the .25/'06, .270 WCF... Hot, hot, hot. Not the best for barrel life. No prairie dogs. But probably top quality and with reloaded ammo, equals the likes of 7 Rem mag, Weatherbys???, etc. I think it said he was an immigrant from Greece? Anyway, sickness in his youth left him weakened and he died fairly young. (50's?) Not trusting others to NOT exploit his work he had his wife burn his papers, etc. You may have a prize. No idea value. luck/happy trails.