Now, ever since I read MechWarrior 2 way back in high school, I've a had a thing for the Mauser 960. Looking at the availability for it in A Time of War, I see that it's got ComStar faction, with a tech rating of F in the era I'm building for (3049.) Now, if you are trying to obtain an item outside of its normal faction you increase the ratings by one. This would then push the Mauser up to a tech rating of X, which is flat-out not available. Does this mean that, since Equipped at 10 TP only goes up to F/F/F, you cannot obtain a Mauser 960 unless you are ComStar faction?
Yup, that's how it goes. Its not that surprising, the Mauser 960 was considered extremely rare outside of ComStar, and some sources point to them being rare inside ComStar as well. Its going to be an item that you need to talk to your GM about, maybe arrange a backstory for it, rather than being an item that every PC could pick up (albeit at a hefty cost in Equipped points).
And just for the record, the tech rating doesn't increase. For Affiliations other than ComStar (in this case) the Availability and Legality increase by 1 each, while tech remains the same. So that E/C-F-D/D Mauser become E/D-X-E/E. So yeah. The availability for the Succession Wars era is beyond factions outside of ComStar, by the rules. Again, ask your GM, maybe you'll be able to convince him with a really good story.
If you want a really funny example of how Equipment ratings and Affiliations work, look at the Ebony Assault Rifle. Its a F/X-X-E/F weapon, with a MoC Affiliation. However, the Equipped Trait tells us that any Periphery character must reduce the Tech Rating Level by one. So even if you spend the points to buy a +8 in equipped, the F Tech level that +8 gives you becomes an E. Which means that MoC characters can't get to the F rating to buy the Ebony Assault Rifle. And since all other factions other than the MoC have to add +1 to the Availability and Legality ratings, the Ebony becomes F/X-X-F/X. Which means no one can start with the Ebony Assault Rifle if they follow the rules exactly :)
Of course, situations like these two are why RPGs have GMs, and players write up backstories to try to get goodies like these :)