If memory serves Noel, didn't you have one for sale a couple of years back?

Answered...
I'll re-copy it here;
** remark ** it's only for the late FN and Mark X actions, not the "military" ones.
"F" = two pieces
"FI-S" = one piece, "Short mount"
"FM" = one piece, "Long mount"
"FI-U" = one piece "Micro-Dial"
Hole spacing is the standard Weaver pattern means 0.850" front and 0.500" rear, distance between inside holes is 3.800" (means the two holes facing each other, front and rear bridge).
Kool, you better stop by so we can look at your 4100 and make a trade.



























