Open Drive Top Loader/ No Serial Number??

[GaryU.]

Picked up this three speed open drive top loader this past Saturday about 25 miles from my house. Upon inspection I found it has no serial number stamped above the inspection cover. One might conclude this is a service replacement part except this is the fourth one I've found over about five years and NONE have had a serial number stamped on them. These were used on 1/2 ton pickups from 1942 to I think 1952. Any thoughts appreciated, hopefully someone has the knowledge to share. Thanks.

 

[cas3]

After 48 they used a different place for the numbers. Cars use a different trans, but pickups continued with the 78 case with no numbers on them

 

[GaryU.]

Thanks for the answer.