HELP PLEASE... for those with better eyes than mine.

The cover (below) is from from the 1851-1855 period. The cover began life as a Stampless cover, at a "5 cent Unpaid Letter Rate" (effective 1851-1855), addressed to Copenhagen, N.Y. on April 3, 185?.
The cover was received in Copenhagen, N.Y., where it received the "5", indicating unpaid, it had a Scott 10a applied to pay a "3 cent PAID" Forwarding Rate to Watertown, N.Y. The Sc# 10a is tied by a light green 33mm Copenhagen, N.Y, on APR 6. The Sc#10a bears an secondary "squiggle" manuscript thru the middle of the stamp in the same color ink as the manuscript "forwarded" and "Watertown", as verified under fluorescent light. I believe the purpose of the secondary marking on the Sc# 10a was because the Postmaster at Copenhagen felt the cancellation was too light on the stamp and the "squiggle" ink marking was to prevent the stamps' re-use.


SO, if any recognizes this manuscript marking, I would be grateful for your input or suggestions.
Thanks for your help in advance.
Best,
Hal