The extra ring or rings was common on vintage engines, especially ones with oil control problems or extremely long skirts. The trend since the 40's has been 3 rings with the rings becoming more narrow.
I didn't see the article, but the jig is most likely a torque plate.It gets bolted down to distort the block the same as when it's fully assembled or it may be something associated with boring Flathead V-8's Torque plates are often used when boring engines , most are bolted to the top of the block to simulate head bolt stress.
