George Worthington was a firearms dealer in Cleveland, Ohio, 1890-1935. Their Harvard branded shotguns were made by Crescent Fire Arms Co, 1893-1930.
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DROS is Dealer's Record of Sale. That is identifying information on you and the firearm.
out of business
The HK USP is a semi-automatic pistol developed by the German company Heckler & Koch GmbH. Information on the firearm and its variations can be obtained from the company directly or through publications such as Guns and Ammon.
I find no listing for "London Arms Co." Provide more information or take the firearm to a local gunsmith for a professional appraisal.
It is rare to find a modern firearm (last 50 years or so) that has NO markings at all. It is possible that those markings may have been removed from a modern firearm. Without some additional information, such as the type of firearm, we do not have enough information to offer a real answer.
Such information is not made available to the general public.
Changes according to what is popular
The Marlin Firearm company has owner manuals for the different firearm models that they sell. You can find downloadable versions of the manuals on the company web site.
Brownells sells firearms and firearm accessories.
Not enough information to answer. If you will post ALL markings, and a description of the firearm, we'll try to give you an answer. S&W Ctg is a partial caliber, not a make of firearm. Several companies made firearms for cartridges named by the S&W company.
Need more information, such as type of firearm, etc.