I - (it's an "I" not a #1) It means you have the International package 31 - 31' long (Sovereign) T - Twin Beds 9 - 1969
2 (?) - Are you sure this isn't a "J" or a "S"? "J" would indicate it was made in Jackson Center, OH & "S" would indicate it was made in Santa Fe Springs, CA 179 - 179th one made
Serial number? Not so sure about that. Was J180fh on a separate line on the badge to the right of your door? Something tickles my memory about how that defines something different...
The 179 is called the sequential production number. This sets it aside from other similar length/bed configuration models made that year. And therefore InsideOut's post best defines what actually is the VIN of your unit.
Does I31T9?179 actually show up on your title? A 2nd location of the VIN can sometimes be found stamped on the right side of the A-frame up front.
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