Hi Rick, Welcome to the forum, and congratulations on your Luger.
You can get some estimates of retail (replacement) value of your Luger by looking at the Simpson listings. These would be good for insurance purposes.
http://www.simpsonltd.com/index.php?...49da19d214b5e3
Your 1900 model Luger should have cupped toggle knobs and a leaf (rather than coil) spring. Please confirm this.
Condition and marking details are quite important in Luger collecting. That's why it's very difficult to give you a ballpark estimate of value without seeing the pistol.
Marc
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