Remove blue/black?

[Marplot]

I recently landed a prewar Collath drilling. 16x16 -- 9.3x72R The seller decided to renovate it. Did a great job on the stock! BUT The metal sucks. It has case hardened receiver and some of the metal is now black.

How do I remove the blue/black? It is very well done, even and smooth, but it hurts my heart to know what is under it. The trigger guard and underlever are horn and will also pop when I get it back to where it was.

 

[Marplot]

Answered my own problem. Plain vinegar does the job easily. Soak part for about 5-10 minutes. Neutralize the parts with baking soda in water.

Rinse thoroughly in warm water and done!