My condolences on the passing of your family friend.
Your Bubble serial number 293 is right at the changeover point between the 1955
California built bubbles. The Official Mobile Home Market Reports (blue books for used travel trailers) for the mid-1950s do not list any beginning serial number for the 1956
Airstreams in general or for Bubbles in particular, and neither does Airstream, Inc., so its unknown at what Califonia serial number the 1955
model year stopped and the 1956
model year began.
Some people think the Norwalk, CA factory began annual Bubble production at a round serial numbers: 200 for 1955
, 300 for 1956 and 400 for 1957
. Others look at features, like straight vs. teardrop fender wells. It's the serial number which determines the model year, not the features, yet in some states trailers were given the year in which they were first registered and licensed, as opposed to manufactured. You likely are not going to find any hard proof of your Bubble's model year. If I had to guess I'd guess your Bubble s/n 293 is a 1955 model on the theory 1956 California Bubbles began production at s/n 300, and your s/n is below that round number.
Anyway, WBCC big red number 609 was first assigned to Doris Moore, 16 W. Lemon Ave., Arcadia, Calif. when she joined the club right after she purchased her first Airstream, which I bet was your Bubble as the timing is right. Doris went on two WBCC Caravans, the Winter 1955 West Coast Mexican Caravan and the Six Months 1956 European Caravan. The later caravan is well documented with numerous photos in the June 1957
issue of National Geographic magazine. I imagine she took your Bubble on those two caravans as she appears to have been single and the Bubble would have been just the right size for her and for overseas adventures.
Congratulations on acquiring your Bubble. Check New Mexico motor vehicle laws to learn how to get a title for your Bubble. Good luck!