Craig,

Overall the details look great, in particular thank you for coding the Form fixed field "r" -- something many of us forget to do when working with things like blueline prints, etc. let alone other kinds of reproductions. Good job on including $e in the 040 as well. Some suggested changes:

a. Call number? Not required since you do have at least a class number in the 052 but feel free to add even a non-G call number using the 090 field or an 050 _4 G-class number

b. 246 field, include the remainder of the title even though the changed word is the second one in the string for clarity about what the map is about

c. Where's the coordinates in 255$c? You have them in the 034 field, since you are creating a full level record you need to have matching ones in 255. Also, I strongly recommend changing those in the 034 field to decimal degree format, i.e., "machine readable" format so that this record can be repurposed in other schema contexts. See the map cataloging best practices document that MAGIRT approved in Jan 2021 for guidance, it is arranged by MARC field:  https://www.ala.org/rt/sites/ala.org.rt/files/content/MAGIRT/Documents/MapRDABestPractices2020_Final.pdf

d. 264$b: please add "Company" and closing square bracket at the end of this publisher information

e. 300$b: while what you put here is not "wrong" cataloging practice has always been to assume black and white and not put that info in this subfield but if in color to be explicit about that; this also applies to your first 500 note. 

f. 775 field: here's probably the one item that really needs attention! You have your relationship statement but nothing else, i.e., what's it a reproduction of? If you do not have information about the original then use what appears in your record. You have nothing to go on so you have to assume the original has the same title at least. Scale is the same according to your message. Etc. So:

775 08 $i Reproduction of (manifestation): $a Denver and Salt Lake Railroad Company. $t Denver & Salt Lake Railroad "the Moffat Road" : the most direct route to the heart of Colorado's tungsten field. $d [Denver, Colorado?] : [Denver and Salt Lake Railroad Company], 1915? $n Scale approximately 1:200,000. 

and if there happens to be a record for the original digital copy you could add $w OCLC record number info.

Other map catalogers PLEASE jump in if I missed anything or made any incorrect suggestions, I haven't done a P-N record in quite awhile myself!

Paige