R vs L shirts from US dept stores (Neiman Marcus, Saks, etc)

[Miran2]

Does anyone know what the difference is between, say, 17R and 17L shirts, made by Italian houses for US dept stores like Neimans?
Is the shirt length just longer and the sleeves longer? Or are they cut differently, with differently shaped collars, longer armholes, and buttons placed differently?
There is no R vs L in shirts sold in Europe...so do they specifically make different cuts just for the US market, but in the same size?

Any advice gratefully appreciated.

oh dear

 

[deveandepot1]

IME the difference between an R and L is just the length of the shirt and sleeves.