I would look into and reasearch more deeply on what EXACTLY the Brits applied to these lugers. Enamel can be just a generic term. If and that is a big IF you can find more info into exactly what it is it may be more easier to find what will remove it and it could make it easier for you.
On a side note and I won't harp on it but I will say my piece, that finish was part of the Lugers history, but since you are past that point with the Luger I will add my Good Luck to you in your project and I hope you will keep us posted with the outcome.
