If these are indeed original items from Congressional Pension files, they were stolen from the National Archives.
However, if they are only Declarations for Pension, they could be the original County Court documents or the copies of the originals that were made and retained by the Court Clerk.
I know of instances where originals survive in County Court records, and certified copies were sent to the Pension Bureau.And, conversely, where originals were sent to the Pension Bureau but copies were made and retained by the County Court Clerk.
In quite a few places old original documents have been sold or given away or thrown away due to the expense of storing them.
But yes, in my view, they definitely should be retained in an appropriate archive.