I have not looked closely at any Hemis, but I'll take a stab at the numbers;
E - Series (model year, 1969)
VN is likely MN?
426 - 426 CID
2723 - Engine asssembly date from the 10,000 day calandar, Jan 10th, 1969
20682 This number is one digit too long, can you look at it again or post a photo of the whole stamped area?
The above number is called the Engine Serial Number, the VIN number should be on the passenger side of the block.
Since it is a '69 block it has to be from a B-body if it has a VIN on it.
Cool find for sure.
Barry