The process in choosing a prototype

[Simon Moore]

Hi all,

I wasn't sure which part of the forum to put this in so thought it might be best here. MODs if you think it should go elsewhere please feel free to move it. 

Whilst i was at Haworth today buying my new Bachmann class 47 i was looking at all the models & wondering how they got there. What i mean by this is what exactly is the thought process in to choosing the next production model ?

My class 47 is the Scotrail version in Bachmanns current range but why exactly that number/livery. Do manufactures have a certain process in choosing a specific loco or do they just pluck one from a hat so to speak ? Class 47's had 512 examples made & in many different livery's so why   specifically was my 47 produced as a scotrail loco & why Sir Walter Scot ?

Cheers

Simon