Let me clarify a few things that led to our claim:
1. The 1st EPI was founded within the Napoleonic Wars era linebattle community in December 11th 2010 for the Mount and Musket mod. We are aware that there are video gaming communities which may play the Napoleonic Wars DLC that existed prior. These groups, however, were not a part of the foundation of the community.
2. Despite the fact that we claim 1st EPI was founded in December of 2010 we can trace our origins to the 7th Prussian Foot, a regiment in the Age of False Innocence mod which existed prior. This regiment was one of the earliest examples of musket line drill in Warband.
3. The 1st EPI has been continously and consistantly active since it's founding in 2010. In fact, we still retain several members that joined prior to the release of the Napoleonic Wars DLC, including a founding member.
4. As far as we are aware, we have outlived all other, older community founding, Mount and Musket/Napoleonic Wars regiments.
I must apologize in saying I have never heard of the 10thRM. A quick search has lead me to the 10th Royal Marines which have a post on the Taleworlds forum which states they were founded in 2012.
I would be interested to know if this 10thRM did exist in the "Good Ol' Days". There are not many of us left