Help ID old Raleigh roadster model and year.

Hi, I bought this old Raleigh about 20 years ago to fit a vintage cyclemaster engine, but ended up going with an old GPO bike.

So I'm looking for some help in identifying the age and model of this old Raleigh roadster type bicycle. The frame number looks like it's 105896 which dates it very early, but apparently Raleigh reused frame numbers so this is very little help. There is also a random small O stamped on the bottom bracket.  

After some hours on google my findings are that as It has a brass head badge with the offset rivet showing the herron eyeball it is 1930's or before. The rear frame triangle bolts on at the top and bottom, and there are horizontal dropouts. It has a hole for a missing oiler or grease nipple on the left upper bottom bracket, and seems to me to have the more laid back head tube angles of the earlier bikes. There are no braised-on chain guard mounts and the hockey stick chain guard is something I am thinking of adding, along with the mudguards if I can find some way of fitting them to the forks and dropouts. It has a band on Sturmey Archer pulley wheel (no braised-on frame lug) which confusingly makes it a later model , but the brass top tube SA gear changer is an early item. The 40 spoke Sturmey Archer AW 3 speed is dated 1954, and the 32 spoked front wheel is made by Philips. There are no mudguard eyes on the D shaped fork blades, but all these features may have been added as replacements over the years. 

So, if anyone can help me make sense of these contradicting  features I would really appreciate it.