Miller - thanks kindly for the information
Like I said, pin fires are not in my knowledge base. Looking around on the Internet, these pin fire hammers have throws from 42mm to 56mm.
Background on the Hollis: My friend does not own a pin fire and his arm was twisted for $100 to buy the Hollis. It is NRA Antique VG and is missing the right hammer. Not having a pin fire, he wanted to add it to his collection of long arms (vintage 1850's to 1930's)that number over 800 pieces. His latest project is a Zulu shotgun that was factory converted to rifled bore. He's in the process of making rounds for it and then a test firing for an article he is going to write
Of the shotguns in his collection, my favorite is an '94 Remington C Grade that looks like it just came out of the box. It's gorgeous