Nice examples of Patriotic covers. I suspect they were used in the mailing of telephone bills back in the day, so quantities out there may have been massive ... the question is how many thought to save these little pieces of history.
The International Postage Meter Stamp Catalog references the metered cover shown as a B5(B)(d) variety from the Pitney Bowes "CV" Meter that was first put into use in 1934.
In case anyone is interested what the 1942 version of the War Savings Certificate looked like, here's a $5 example taken from a current
ebay listing:

Note the issue date on the Certificate is 15-2-42. Since the Certificate matured in 7-1/2 years you will see the owner penciled in the maturity date of "15-9-49" (although I would think the correct maturity date would have been "15-8-49").