Is there any way to revive engraved initials on old tools to make them readable again? I'm battling a dishonest roommate!

I think you've answered your own question here. The police have confirmed it's a civil matter and you're talking about some of your fathers tools. Take them back and consider dropping them off either somewhere you trust or at an engravers to have them re-engraved.

If they're your tools, they're your tools, irrespective of what anyone else claims. Hopefully if anything comes of it, you get the same officer who told you it's a civil matter attending.

Not if they are chrome plated. If they are bare steel , dilute nitric acid may show something ;Try 5 % nitric in ethanol . That is a little stronger than "nital" , the standard steel micro etchant. It will not touch 13% chrome and probably not 5 % chrome which are possible but unlikely steels for tools. I guess I should add, if they are not chrome plated , dropping them into strong acid baths can cause stress corrosion cracking of high strength steels like hand tools.

I will describe a procedure I use to engrave art blades I do as a hobby. It is not complex but requires quite a few steps to have it done properly. First, forget about powertools like a Dremel because they need a very fine muscles control to avoid the tool tip to keep jumping around, in other words, very difficult to control the strokes.

You need:

a) A DC power supply between 5 VDC to 12 VDC, a regular 14AH battery charger will do very well, also a car battery but they are too heavy. You need it to have at least 1 Amp output.

b) A couple of crocodile clips (https://en.wikipedia.org/wiki/Crocodile_clip#/media/File:Alligator_clip_442.jpg)

c) Cotton balls

d) Water and table salt

e) Paint, wax, wax crayon, anything you can use as mask and can be scratched

Procedure

a) Clean the metal piece you want to engrave very very well, if you can sand it to bare metal better. It should not have rust, or very little rust, but doesn't need to be mirror polished.

b) Apply paint to the area you want to engrave. You can use nail polish enamel which dries fast, or spray can paint. Also you can heat it a little bit and rub wax crayon, those colorful stuff used to draw by kids. You need to mask everything you don't want to etch!

c) "Carefully" scrap the coat you made in point b), with a very thin piece of metal...a nail, a hard steel wire, a dremel tip fixed in a piece of wood stick, etc. So you draw the figure or letters you want to etch, by scratching the coat.

d) In a plastic vessel prepare a mix of table salt and tap water: something like a couple of table spoons of salt in 1/2 liter of water, stir it very very well.

e) Attach + lead from your power supply to the tool using the crocodile clip

f) Attach a cotton ball to the - lead from your power supply by using the other crocodile clip.

Now the fun

a) Turn the power supply on

b) Wet the cotton ball in the salted water but don't let the water reach the crocodile clip or otherwise it will be also etched (unless you want to discard it later)

c) Rub the coat where the scratches are, with the wet cotton ball...softly, not really rubbing but something like sweeping it from one side to the other...

d) Do it again and again. At first you won't see any differences. About 1 minute doing it you will see the cotton getting dark: that's metal getting off the piece. Keep doing it and you will be able to see the scratched draw getting more and more deep. When the cotton gets very dirty, use another new one.

This won't produce a really deep groove, maybe 0.02" to 0.03" but it will end up "very noticeable".

This is called electroetching and doesn't use acid or toxic stuff. When done properly, you can do wonderful things with it :)

I won't post one of my pieces here...since this is about cars and mechanics stuff, not blades.

Example from google search: Sometimes people would just stick the "artwork" made in cut vinyl adhesive....

https://www.youtube.com/watch?v=qb-UmxS3PIE