According to Richard Paine's A Review of Graflex, the 5x7 Speed Graphic was produced up to 1941 with little of the updating found in the Anniversary model. If the tubular finder is original, your camera was made in 1939 or later.
It's not original. I found the original flip-up gunner style finder in one of the parts boxes, the holes in the body lined up perfectly. I took off the tubular finder about an hour ago.