1967 Barracuda fastback fender tag deciphering

Remember this car?
Scheduled Production Date was 4/25, Actual Shipped Date was 5/2.
GG decoded it as:

M2 Designated Line 2 Build After 118 SPD

My guess is 118 SPD = January 18, Scheduled Production Date.
I checked a number of cars I kept data for and it seems to check out.

What is significant about January 18?

37747_117102421670150_100001111775214_103493_407042_n.jpg