This is kind of interesting and something I'll try to respond in such a way as to at least make some sense, or sound like Duh tell me something I don't already know.
I am assuming your trying to distinguish between GS, nickel plated and possibly brass.
German silver will not have the look of a chrome plated bumper or mirror (nickle plated) unless it has been freshly buffed and polished, and even then a trained eye can tell the difference.
Any scratches dings/dents in a solid german silver reel will have the same color as the remainder of the reel with no brassing showing through.
Although German silver will pit with severe exposure to the elements the pits will not show any brassing in the pits
Some GS reels recently bathed in vinegar might show a rose colored hue.
It is my understanding that some german silver reels were actually subject to nickel plating while others may have been nickel silver plating over brass. Others can expand on that.
Many models were only made in GS while others were made in both GS and brass plated.
I've seen a few reels listed for sale as brass knowing that under that 100yrs of patina was german silver. Also seen reels listed as german silver that were obviously not due to the coloration or style of the reel (never made in GS).
In summary, short of testing the metal in a lab I would recommend viewing as many GS reel pics and, better yet in-person, as well as researching what reels were and were not offered in GS and comparing them to the more common brass plated and brass reels you come across.
If there is a particular reel your are interested post a pic and I'm sure you'll get multiple responses.
At this point, I can tell just by looking. The more reels you handle the easier it gets.
Early on, when I wasn't as confident, I would open the reel up and put a short scratch somewhere inconspicuous on the interior and then look at it with a loop. If I didn't see brass I knew I had German silver.
Hmmm what about white brass which has a greater zinc content. The properties allow greater strength BUT like you noted the only true way of knowing is through essaying. It to can appear as nickel...
Wanted Ultra rare salt water reels including big game as well as unknown rare surf reels!
Here is a very non-scientific answer. German (nickel) silver reels look like German (nickel) silver reels. I collect J A Coxe reels for example. If you sit a Coxe 10-3 next to a Coxe 15 it is easy to pick out the GS reel. They can both shine but the GS reel always has a "warmer" look. Not as shiny, but just a softer, warmer shine. You can polish a GS reel like your wife does (at least in my case) does with the any silver or brass things in the dining room. She never brings chrome polisher, she use silver and brass polishing products.
Wayne Benson
ORCA Member, 2009
Waynesreelcollectibles.weebly.com
Thanks for the replies. I just going to take the reel to my dad, he is a custom knife maker and should be able to help me with this reel. Hopeful someday I will be able to tell on my own. I will just have to keep buying more reels until I can tell the difference.