N&W Emblems

[NW Modeling List]

Hello N&W modelers! I hope there are a few "old timers"  that worked for the N&W or N&W scholars that will be able to answer these few questions
I just bought 6 n scale N&W Locomotives:2 Atlas Trainmasters (#165, the other un numbered) both have the "hamburger" emblem... a gold circle with gold italicized N&W within. It also has" Norfolk and Western" printed in gold letters across the side.1 Atlas RS3 (gold #300) having the same N&W emblem and print as above. 1 Atlas GP9 (white #752) having large white block letters NW, no name is printed on either side.1 Atlas RS11 (white #341) lettered the same as above.1 Life Like SW 1200 painted blue. The emblem is of the "hamburger" style, a gold circle but... has an almost solid gold interior with a space in the middle with the same color gold N&W lettering. 
My first question is WHEN...meaning year...did these different paint schemes come about? What my understanding is that when a new CEO came into power, he changed the paint and lettering scheme. I'm trying to establish an era that will encompass all six of these locomotives. 
My next question is very similar, it's about N&W cabooses. 
I notice that there are blue cabooses as well as red. So far, I have 5 Atlas red cabooses. Two seem to be of the newer type (#55777 and 557780) that have the large wide white NW lettering in the middle of the car. One of the  older types (#562764) are lettered with a smaller white NW near the end under the cupola, and the other older type (# 562733) has the hamburger emblem similar to the SW switcher only done in white locate in the same place as the other older caboose mentioned above... near the end of the car under the cupola. 
Same question... When. I am guessing that the time line will be similar to the locomotives. 
One more question concerning the Trainmasters... From my understanding, they originally belonged  to other railroads that the N&W acquired. What year did they take on the N&W lettering?
Thanks for your help,Bill Capranica
PS: If "my understanding" is incorrect, please enlighten me to the truth.   		 	   		  
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