Borge Mogensen SM122 vs 150 for Soborg Mobelfabrik  

There was no Søborg Møbler model 150. What I see in the above photos is model 155.
Can you post a photo of the chair in question and the measurements?

Edited.

thanks @leifericson sorry that 150 was a typo, meant to type 155
The picture of the group is 155's pulled from 1st dibs, I believe.
Of the 2 chairs in question; the one with wooden floors is from Antik Modern and attributed as SM122.
The other chair, picture outside measurements are 30 inches tall to the back, 17 inches tall at the seat, the back is 18 .5 inches wide by 11.75 inches tall. The seat is 19.75 inches wide by 15.75 inches deep.
These measurements are slightly different from what I have seen for 155s and wondering if it might be a different model? a knock off? or what?

I thought I would have measurements in one of my Søborg catalogs, but there are no measurements for the chairs in any of the catalogs. I had not realized that.
The SM 122 has vertical legs and a much smaller backrest. I suppose it looks a little bit similar. Antik Modern is wrong with the model number.
I would not think that there would be knockoffs off this design.
And I would not be too surprised if the dimensions were a little bit different over time.

Thanks @leifericson !
That was my thought (in regards to the vertical legs and smaller backrest) as I saw some chairs perhaps attributed to SM122, but couldn't nail anything down.
I was a bit shocked because the chair I am interested in has slight difference in measurements from the 155, but generally speaking it looks pretty similar and assume it is the variation of dimensions over time that you mentioned.
Hopefully it is still available to add to my collection!
Thanks!