For reference, a faked Navy G Date was picked apart on Jan's forum some time ago, with good comparison photos...
http://luger.gunboards.com/showthread.php?t=21332
I'm no expert, but I'd expect the spare mag to have a "+" ? And, the stick eagles look different (right one looks wider?) (edit: and as Tom points out in the post below, stick eages are not correct for G Dates)
The eagle over m on the strap doesn't look good.
Looking forward to the expert opinions... I'm always learning too.
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I'm looking for a D suffix DE154 G Date mag. The closer to #457d the better

PM me if you have one you are willing to sell, trade, or if you have a lead