i'm gonna have to agree with tommy. the serial number looks to me like A06814426A.
here's a breakdown of silver certificate experimental notes:
experiment 1, 1933
series 1928A, 1928B
X - B, Y - B serial number blocks (experimental)
Z - B block (control group)
experiment 2, 1937
series 1935
A - B block A00000001B-A06180000B (experimental)
B - B block B00000001B-B03300000B (experimental)
C - B block C00000001B-C03300000B (control)
experiment 3, 1942
series 1935A
S - C block S73884001C-S75068000C
S (experimental, red S for "special paper")
S - C block S70884001C-S72068000C
R (control, red R for "regular paper")
all the tests were inconclusive. the experimental paper blends showed wear at around the same rate as the regular paper blends.