The tank/loco is Lionel #203, is suspect Type 1 from 1917. Type 1 was olive (as yours) and had “Lionel Manufacturing Company” on the bottom tag (as yours). Type 2 were battleship grey, and Type 3 (1918 through 1921) were grey with a “Lionel Corporation” tag. Your #203 Type 1 is very rare, indeed, with a hefty price suggestion in the Lionel guides.

2. The #203 was teamed up with a pair (2) of the #900 Ammunition Boxcars to constitute freight set #214, which I believe is what you have, circa 1917 or 1918. The ammo boxcars were grey (rather than olive), I think confirmed by your first photo. Current pricing ranges from $120 (each) in good condition, to $340 in excellent condition.

3. As side notes …

a. The #200 ammo cars appear to be similar in form to the #800 boxcars, with the #900 being much more rare.

b. The #203 loco/tank was also sold as set #215, which included a pair of baggage cars (#702), rather than the ammo cars.

4. Re: paint and finish. Absolutely do NOT attempt to strip off any paint, rust, etc. Leave as original an untouched as possible.