I need a little help figuring out a transmission ID pad. I was expecting to find something that resembled the serial number but instead I found this:

392093L2622 7135

How do I determine if this is the original trans

It is in an early build 69 GTX,
Sequence number B157098

you are missing some numbers there , that string is on the pan rail on the drivers side of the trans , it should start with PK , that should be PK289209. The number you are looking for , the VIN , either full or partial , is on a raised pad on the passenger side of the trans on the bellhousing area .

check your numbers again

transmission sounds like - PK2892093L
assembly date - 2622 = Tuesday, October 1, 1968
unit number - 7135

The assembly date (if 2622 is correct) appears appropriate for a '69 GTX assembled in St. Louis & "scheduled" for the second week of October '68.

What is VIN# of the GTX? VIN# should be stamped on pad RH side of transmission bellhousing.

What is SPD of GTX?

I was wondering if some of the numbers got cut off. The first number right at the corner looked like a 3 but was right at the edge so and 8 would work as well. I will need to spend some more time on my back to look up the other side of the trans to find the right numbers.
The SPD was Nov. 28, 68 out of Lynch Road