Greetings Elaine and Bohdan!
Welcom to the forum and the world of Vintage Airstream ownership!
RE: WBCCI Membership Numbers
The numbers above the front (and likely the rear as well) window are assigned to members of the WBCCI. If you choose to join the WBCCI (Wally Byam Caravan Club International), you might request the number currently on the coach if it is available (the number stays with the member as long as he/she is active in the club) - - inactive numbers usually become available after two years of inactivity. To learn more about the WBCCI, try the link below:
Wally Byam Caravan Club International
Since your coach is a Vintage, you can get even more enjoyment from your WBCCI membership by joining the Intra-Club otherwise known as the Vintage Airstream Club. You can learn more about the Vintage Airstream Club at:
Vintage Airstream Club, An Intra-Club of the Wally Byam Caravan Club International
RE: Tracing the lineage of your unit:
There are many Vintage owners who wish to do just what you are wishing. Unless conditions have changed, Airstream doesn't provide the information nor does the WBCCI. The one thing that you can find is the build location - - it is part of the serial number. I am not certain, but I think that by '73 Jackson Center, OH was likely the only assembly location for Airstream but I am honestly not certain. There is a possibility that the DMV may assist you in doing a title search (for a fee of course) but the search will only include registered owners in the jurisdiction of that particular DMV. I know that such searches were possible in Illinois through currency exchanges when I purchased my '65 Dodge - - it had an interesting background of ownership. Sometimes it is possible to learn a tremendous amount from a recent owner who may be able to point you in the direction of earlier owners - - there are times when some things just happen out of the blue - - shortly after I purchased my Overlander I was passing through the town where the son of my family's friends who had introduced me to Airstreaming/RVing lived. I happened to be towing the Overlander - - he took one look and exclaimed - - "Where did you buy mom and dad's coach?" - - he identified it by the drapes that his mother had made for it shortly before it was sold in 1980 (so I had a shortcut to much of the coach's history as the previous owner had filled in the blanks for the most recent two owner ahead of him and with the contact with the first owner's son, I was able to fill in the balnk with the second owner's name. Tracing the background of your coach can be nearly as challenging as working with family geneology. The WBCCI numbers currently on the coach may help you contact the most recent holders of the numbers which might be a first step to learning more about your coach.
RE: Airstreams in Canada
While I am not aware of numbers, there are always a large number of Canadians at the WBCCI International Rally. There are a number of very active WBCCI units in Canada - - I have several friends who live near Brandon Manitoba and are active Airstreamers and WBCCI members.
RE: Resealing front window
It depends upon what you mean be resealing the front window, and I am assuming that it is one of the side "wing" windows. If this is the case and you mean reseal as in a thermal pane window that has separated and now has moisture between the panes, there isn't an effective repair - - replacement or there are solutions involving "breaking-out and removing the inner pane" that several have tried. If what you are asking involves sealing the mating surfaces of the window flanges to cure a perimeter leak - - this is a very doable proposition and the usual product of choice is Alcoa Gutter Seal which is a "wickable" product that leaves almost not trace on the surface. There are at least two competitive products but I am not certain of their names. It is also possible to use a VERY thin bead of Vulkem, but it is difficult to manage without some practice.
RE: Front Window Rock Guard
This was optional equipment, and if the coach didn't have "wing" windows it wouldn't be such a great concern. The "wing" windows are the reason the rock guard is often considered necessary with the newer coaches as these windows are quite costly to replace when compared to the cost of the nearly flat glass found in the center window. Without the rock guard, it is possible to open the drapes front and rear allowing you to see through the coach using the center interior mirror in your tow vehicle (assuming that the tow vehicle is high enough to permit this - - works with my Suburban and the pickup that was its predecessor, but doesn't work with my Cadillac or Dodge. The rock guards have been available in a number of styles, and there is a current style that will work with your coach; just be prepared for the price of the part plus shipping - - may very well run nearly $700 for the part plus shipping. I was fortunate with my Argosy Minuet as I needed a rock guard for it, but was going to have to modify one as it is 8" narrower than other Argosys and Airstreams - - mentioned this to my Airstream dealer and he indicated that he a a rock guard in the attic that had been damaged in shipment and was going to need to have the center material replaced - - the damage was such that the modifications will require cutting away the damage so a very good deal was struck - - sometimes it is possible to find one of these guards through an RV salvage yard - - again, shipping can easily surpass the cost of the part.
RE: Towing an Inactive Coach
The greatest concerns in towing a coach that hasn't been on the road for some time center around the running gear. Of particular concern would be having the wheel bearings serviced and brakes checked out (in my area this typically runs about $50 per axle). The second concern would be the tires - - even if the tread appears good, they are likely old enough to be dangerous as a result of dry rot and weather exposure (many, myself included, routinely replace their trailer tires every fifth year regardless of mileage or tread wear). The third concern would be getting the necessary running lights functional - - turn, tail lights, brake lights, running lights. Be prepared as the trailer end of the umbilical cord will likely need to be rewired to match the moder standard utilized with current tow vehicle setup - - I would suggest having an extra trailer end that matches the receiver on your tow vehicle to insure that all will be compatible - - rewiring sounds worse than it actually is - - I am not a do-it-yourselfer, and I had the trailer end rewired on my Argosy Minuet in less than two hours. You will also want to determine just how much hitch equipment is included with the trailer - - you may need all or just certain pieces - - depending upon your tow vehicle, you may need to be prepared with a deep drop draw bar compatible with any hitch equipment being included with the trailer - - this is a near given if you happen to have a GM K1500 or K2500 series vehicle for towing. If no hitch components are included, you will need to choose a weight distributing hitch with adequate drop to get the ball height in the vicinity of 18.5" (a more precise figure should be in the owner's manual but the above should be very close) - - then there is always the question of sway control - - each person has his/her own favorite, mine is Reese Dual Cam Sway control but there are many alternatives out there and the selection depends to some extent on the hitch you happen to be using.
Good luck with your new acquisition, and again, welcome to the forum.