Stihl ms391 47.m vs 49mm?

[smallengineredemption]

I have some ms391s or so I'm told. I haven't run serial numbers yet but one is a 49mm the other is a 47mm bore. Did the 391 come with a 47mm bore ever or the 311?

 

[DND 9000]

The MS 311 has the 47mm bore.

 

[smallengineredemption]

What I thought,