Hi,
Because of all the different countries where TRs were sold, and the different types and sizes of number plates in each, I wouldn't be surprised if most or all of the cars were shipped without any provision for plate attachment, and it was left up to the dealer to do once the car arrived.
Some dealers do a better job than others prepping a car for customer delivery. Many years ago, in another life, I worked at a Chevy dealership doing delivery prep. You'd be surprised how much the factory left uncompleted for the dealer's shop to finalize. We were pretty thorough and careful, but it's different from one organization to the next. (Don't get me started about my local Land Rover dealer... Let's just say I think they use the trainees for some things they shouldn't and, among other things, the running boards on my Discovery nearly fell off on the way home the day I bought it!)
There are usually black or white nylon inserts used for license plate attachment. The inserts are usually square or rectangular in shape and snap into a hole that's punched or "nibbled" into the panel. Generic versions of these can be found in many auto parts stores. They usually stand proud from the surface a bit, too, to prevent the plate from rattling. Oh, and it's important to paint the bare metal edges of the holes before inserting the nylon pieces, to prevent rust from starting.
There are also license plate brackets available from many auto parts stores, if you wish.