What was / is the class designation for UP 3985?

[selector]

Yes, it was a copying error...my apologies.  Since deleted.

[cefinkjr]

Thanks for the info but is that "25" in your post part of the class or an artifact of copying and pasting?

The reason for my question is that I am using a photo of UP 3985 as a desktop background and I'd like to identify it as accurately as possible.  Since I took the photo, I know the location and the approximate time of day.  Now I know the correct class but I'm still at a loss as to the date. 

The 35 mm slide was taken the last time UP 3985 visited the Dallas - Fort Worth area.  I know it was about 25 years ago, soon after I moved here but that's as close as I can come.  Can anyone help my memory? 

[selector]

 

The class designation for 3985, per steamlocomotive.com, is:

4664-4

The article providing this information has a brief history of the UP's acquisition of its Challengers that might shed light on your questions.

http://www.steamlocomotive.com/challenger/?page=up

 

 

[cefinkjr]

My question may have been answered long ago but a search of trainsmag.com didn't find it.

I did find, however, a wikipedia.com page (https://en.wikipedia.org/wiki/Union_Pacific_Challenger) that lists UP:

• 3900-3914, built in 1936, as Class CSA-1
• 3915-3939 (1937) as CSA-2
• 3950-3969 (1942) as 4664-3
• 3975-3999 (1943) as 4664-4
• 3930-3949 (1944) as 4664-5

This would make UP 3985 a 4664-4, but is that accurate?  Did UP revise its classification system some time between 1937 and 1942?

For the nitpickers, I know my brief list above doesn't account for UP 3800-3839 and actually indicates two different classes for 3930-3949.  Notes on the wiki page explain these apparent discrepancies.