Help with Serial Number

[reedj1]

Helping my parents research their old Airstream that has been in our family for 33 years My dad purchased it from our neighbor that purchased it new. The serial plate has the number #1285 My father thinks it is a 48 to 53 model. Any other markers to look for. The interior is in very good condition.

[silverleeper]

Could be a 49 Liner 49Liner.

Pictures would really help though...