That looks like it would decipher as August 21st.
The
K would stand for the plant code which is McKinnon.
Look for a two letter prefix before that assembly date you just listed,like KK or KF.
CRG Reference topic
Look for the rearend casting date at the 4 O'clock webbing position while staring straight at the bullnose cover.
I agree,I've never seen a CON VIN stamped into a rearend axle tube before.