73 H code with space saver rear seat

How rare is an H code 4 speed with a space saver rear seat, I just noticed my 73 has a fold down rear seat, I haven’t really looked it over until today, I’ve had it for about 7 months but was showing a buddy what my next project was going to be when I saw it.
I’m not familiar with the 73 cars, all I’ve had have been 70 and 71 H code cars.