Serial Number Recovery Methods

This thread is a place to discuss different methods for recovering hard to read or tampered with serial numbers without opening Mac OS X's About This Mac page, such as when hardware problems prevent booting, or Mac OS X is not installed.

My story:

I recently purchased a MacBook Pro as part of a civil agreement involving a swap for an iPhone 5, and after trying to read the Serial Number, which had been "scratched off", I could not correctly identify the serial number of the base plate on the MacBook. That and there's about $370 worth of damaged components inside, they stated the wrong year model, and just generally misled me about it, but that's neither here nor there. ( I guess it explains why it was only worth an iPhone...)

The problem:

Initally, only XXX######XX was visible, where X-es designate visible letters, and #-es designate scratched out or illegible letters.

The First Trick:

I rotated the device under the light, finding different angles, but that still left me with a partial serial number (XXXXX##XXX). Those two digits, were making all the difference, and I couldn't with confidence lock in the serial as what I thought it was.

It was at this point I figured I might try something a little more brash.

The Second Trick:

After reading that the serial numbers are laser engraved, not stickers or painted, I got a gel-based ball-point pen, and coloured in over the serial number.

Wiping over the area gently with a paper towel leaves some of the ink in the engraved number, and increases its visibility, similar to inking fingers before fingerprinting: The ink still covers all the rises and falls of the finger, but when light pressure is applied, it pools in the valleys of your finger.

In my case, after trying both of these, I was able to read the complete serial number. If anyone else has anything to add to this, such as adapting this for other devices, or has a different method, feel free to post below.