No more than 50 USD if new in the box.
15-50 USD or so
Sauer, Schmidt, Rohm
While the value of any firearm depends on its condition, the RG revolvers were very inexpensive firearms when new, and are typically worth $50-75 US.
Inexpensive and fair to poor quality.
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Not worth more than 50 USD
No sn data
The Dickson Commander appears to be the same basic gun as the RG model 40, built by Rohm in Germany. Probably worth about $100-$120 in VG condition.
Could be Sauer, Schmidt, Rohm, RG, Gecado, or any of a dozen others.
20-50 USD
Depending on condition, between $50 and $75. These are alloy framed revolvers of indifferent quality.