As an old war mechanic your familiar with all technical machines, such as Pipes, gears, locks, traps, ropes, water power, steam power, etc. You've seen hell and have developed half of the War Machines that causes it, your job was to kill as many people as possible from as far away as possible, but those days are behind you now, yours skills good be used for other things less grim.

Skill Proficiencies: EYES OF THE SCARRED
Because of your Knowledge with machines, you know machines break alot, so you have the choice of being proficient in Investigation.
Your Also a Veteran, War has made it's mark upon you and your horrific past, and those skills never leave, your other choice is Survival.

Tool Proficiencies: LIFT THY TOOLS
As a mechanic for things like Ballistas, Catapults, and Trebuchets It's no Surprise that you'd be Familiar with most Metal Smithing and wood working tools. your proficient  with Most Tools used for such things like the Mason Tool or the Woodcarver tools.

Languages: Soldier Lingo
You may speak tow languages of your choice and you Know Basic Sign Language. 

Equipment: You have a Variety of Tools for tinkering and fixing things, some pocket gold from your travels, and a keepsake from the War to remind yourself ( Input Lore ;-; )