Transmission Serial Number off by 2 Digits

[Cdickjo]

New to the group
I'm restoring a 67 RS/SS The engine and Car Match but the transmission (muncie) is off by 2 digits. As you can see in the pic the car and engine end in 170 the transmission ends in 172. So its 2 units down the production line? Is this probably a mistake at the factory. I purchased the car from the original owner (family). The casting date on the Muncie is Feb67 and the build date on the car is March 67.
Stumped 
I find it hard to believe its a replacement and the serial number is two units different.
Opinions and advise very welcome 

[6667ss138]

Yes, factory mis-stamps happened often.

[Cdickjo]

Thank you.

[bcmiller]

Seems ok.

[169INDY]

Welcome don't forget to snap a pic of you Car & Tag and Post it also.
Cool 4N Car