Early Detroit-built 1956 Dodges used the same format for the cowl data tags as the late 1955 Detroit Dodge cowl data tags. HOWEVER, I don't think that meaning of the codes was the same in 1956 as it was in 1955. That has been discussed elsewhere.
At some point in mid-late May, between May 15th and May 24th, 1956, the Detroit plant Dodge cowl data tags changed their format from the late 1955 style to the style that we know as the 1957 style.
Example June 02, 1955, 1955 Detroit Dodge cowl data tag:
Example 1957 Dodge Cowl Data Tag (for comparison to the later 1956 Dodge tags):
Now for some May/June 1956 Detroit Dodge cowl data tags (PLEASE if you have one that will help narrow down the change, please post in this thread):
(Thanks to those who posted the ones before *OR* sent them to me, e.g. Gary R.):