Obviously the chassis plate and the JAL tag on the RH side of the scuttle is the starting point. I can see the valve cover label on the LH valve cover, it's engine number should match the one listed on the chassis tag. There is also a tag on the main gearbox case right at the flange for the bellhousing and the rear axle is stamped on the bottom of the centersection. Sometimes this stamping can be hard to make out. Lastly, the keys are numbered. If you have the original keys, the ignition will either be an ST or RM code (most commonly, RM). The trunk and cubby box will be an FS code. The trunk key number is also stamped on the bracket that the trunk lock is riveted to. The door locks are also stamped, but the handle must be removed to see it. It appears there are remains of the original paint under the hood (Mediterranean blue), the color code listed on the chassis plate should read "100". All of the above information can be found in the original Jensen ledgers, except for the color code which was only very rarely noted.
You can obtain all of the information pertaining to your specific chassis number from the Coventry Transport Museum, or the Rootes Achieve Trust. These are separate entities and you can easily find them on the internet. These will not "authenticate" the car like a Tac inspection would, but they will tell you if, in fact, it is really a numbers matching car.
I restored a prototype Tiger several years ago and I contacted the Coventry Transport Museum. They were quite helpful and immediately sent me scans of the relevant records via e-mail. There was a small fee that i paid by either Paypal, or credit card... I can't remember which.
The suggestion of having the car authenticated (Tac'd) is also a good one. Having a TAC certificate gives a potential buyer comfort in knowing that they are not buying a converted Alpine! I have had the last 2 Tigers I restored here authenticated. The charge was only $25 (each), but I had to trailer the cars to have them inspected which was a 500 mile round trip.
I am located in Okanogan, Wa. about the center of the state, 50 miles south of the Canadian border.