I have a friend thats and ATF agent and he sent me this today.
I believe if a Form 1 is approved as submitted (without additonal markings,etc) and if approved, would suffice. Here is the recent ruling that relates to your question about marking a SBR. ATF has ruled that additonal serial numbers, etc placed on firearms by every manufacturer in the process is counter productive to law enforcement needs. It talks about licensened manufactures, importeres, and a "non marking variance". They may not have addressed Form 1 requests, specifically. However, when one files a form 1 it is a request/approval to manufacture a specific firearm and contains all the markings to be on the firearm. The form 1 if approved would therefore, be valid and I would say be considered a variance from the "non marking" regulations.
-ATF has issued a ruling that authorizes licensed manufacturers who perform a manufacturing process on the firearms for, or on behalf of, another licensed manufacturer not to place their serial numbers and other required identification markings on the firearms, provided such firearms have already been marked as required and that all of the other requirements stated in the ruling have been met. Read Ruling 2009-5 – Firearms Manufacturing Activities – Identification Markings of Firearms
http://www.atf.gov/firearms/rules/atf-ruling-2009-5.pdf
I believe if a Form 1 is approved as submitted (without additonal markings,etc) and if approved, would suffice. Here is the recent ruling that relates to your question about marking a SBR. ATF has ruled that additonal serial numbers, etc placed on firearms by every manufacturer in the process is counter productive to law enforcement needs. It talks about licensened manufactures, importeres, and a "non marking variance". They may not have addressed Form 1 requests, specifically. However, when one files a form 1 it is a request/approval to manufacture a specific firearm and contains all the markings to be on the firearm. The form 1 if approved would therefore, be valid and I would say be considered a variance from the "non marking" regulations.
-ATF has issued a ruling that authorizes licensed manufacturers who perform a manufacturing process on the firearms for, or on behalf of, another licensed manufacturer not to place their serial numbers and other required identification markings on the firearms, provided such firearms have already been marked as required and that all of the other requirements stated in the ruling have been met. Read Ruling 2009-5 – Firearms Manufacturing Activities – Identification Markings of Firearms
http://www.atf.gov/firearms/rules/atf-ruling-2009-5.pdf