In my book Collectible Elgin - JC Higgins and Hawthorne bicycles, I found an illustration of the bike you pictured. on page 55. Described as "Boys and Girls Low Priced Equipped Elgin Bikes" Same, chain guard, truss rods, light, rack, and skirt protectors. The one pictured has the Steward Warner 'Floating front hub' but in the description it's shown without that hub for $23.95 rather than $25.95. I have a new computer and it's not compatible with my scanner or I'd be posting a picture. Sorry. Anyway, the info you're probably looking for is that the illustration is shown in the S/S (spring/summer) 1941 Sears catalog.
Tried something different. Took a couple of pictures with my Android tablet. See if this illustration doesn't look like your bike.
There are some things in the description for you to look for. The air cooled rear hub and the Troxel saddle. I think that the Alemite lubrication has to do with you being able to purchase a 'grease gun' that would fit the zerk on the rear hub. Hope this helps. Similar bikes in preceding and following years have subtle differences.
A "D" serial number would reflect a 1939 Murray-built Sears bike, (and so on).
Like others have strongly-hinted or implied, a Collegiate is not technically an Elgin.
I like the look of the shiney brass shield Collegiate badges.
Not sure when Murray started using those 1-piece hairpin truss rods.