Searching for hidden or obscured markings

[lexington1]

Does anyone have any good tips or ideas about searching for markings on metal parts, such as signatures, etc., which are which have been obscured through the years? I have had several old guns through the years that have had markings which were nearly gone and it would drive me crazy trying to get a read on them.  One I have now is a New England rifle that I acquired from a gentleman in his 80's. He showed me on the barrel where the signature of J Jennison was which was readable when he was much younger. There is nothing there now, but i still keep trying to make it out. The other gun I have is an Rev. War artillery carbine which has excellent markings on the brass wrist plate, but the barrel regimental markings are unreadable. I have tried on unreadable markings to magnify them with the camera and also take pics in various lighting, with a small degree of satisfaction. Any other tips, suggestions, or ideas?

[okieboy]

 This isn't quite an answer, more of a question about a possible answer. In some of my past work I sometimes did "Dye Penetrant Testing". It is a nondestructive test that shows microscopic cracks in metal. One applies a red dye that has incredible penetrating properties to the metal surface, then you clean the metal surface till it appears absolutely clean, lastly you spray the surface with a white almost powdery developer and if there is a crack there, red will appear through the white. I wonder if anyone has given this a try. I know that engraving isn't a crack, but wonder if tiny tool marks from the graver might help show where the engraved line was. Although a standard kit from MSC would be $111.00, the three components ought as individual cans would only be about $24.00. 
 The same question could be raised about magnetic fluorescing detection.