[OC v2.x] Adding column to admin order list.

Does anyone know of a free sample extension I could take a look at to add one or two columns to the order list?

More specifically, I require "company" and a custom field to be added to the order list.

did you check here for such?
http://www.opencart.com/index.php?route ... der%20list

i.E., this one could do, as sample, to show you the way, at least, I guess:
http://www.opencart.com/index.php?route ... on_id=9554

and this is even 1.5.6.4, 2.0.0.0, 2.0.1.0, 2.0.1.1 capable, it may offers valuable information on howto:
http://www.opencart.com/index.php?route ... n_id=20657

Invoice Numbers:
http://www.opencart.com/index.php?route ... n_id=16423

'Free sample extensions' do usually not exist, exept for possibly free Mod's, usually containing only basic options.
That's, because anyone could make a free Sample to act as 'final solution', and that's not really a usable way to make a business.
Just trying to explain...
You posted this in the v.1.5.x Forum, as well.
Good Luck
Ernie