New to Forum, Looking for info on my new rifle

Hey guys, I am new to the forum here. I have been searching threads to find some info on my newest acquisition. The other day I picked up a Ross Rifle. From what I have researched thus far it is a Mk2 ***, made in 1909. There are no U.S. import marks on it. Condition is fair, I really enjoy unique firearms and the history behind them. I am trying to find out what these other markings mean.

Serial is 173 B6, which I am trying to find out the significance of that.

Also trying to find what these other markings mean.

It is stamped C5 D 12

Then 15 L.H.

Then 74.

I have attached some photos if that helps. If anyone has some info on these markings, or know of a book or some data archive that I look these up it would be greatly appreciated. Thank you again, and I hope every one had a great new year.

Admin can I get this moved to Ross rifle section? Just saw there is a section for this rifle.