Is a Pattern Developing , or is it me ?

[Dan/Panther]

I hope I can explain this right.
I'm starting to notice that condition of phones from the 50's appear to be falling into date categories.
For example, many of the soft shell Beige 500's are dated '58,
I find that as I scan for new phones , many 500's in great shape are dated 1956.

Is this just me or do others find the same type pattern, many other examples,  I just listed a couple  ?
D/P