Hello Tinplate world ... Standard Gauge (as the world knows it) began with Josh Lionel introducing his new 3rd rail line of electric toy trains ...first examples ( trolleys #2 & #1) to roll off the production line ( probably a few 8" work benches) in November 1906 ( don't believe all the stuff you've read before ) .
Of course the standard had no standard ... but repeat the lie long enough and you create a new standard. Standard being a standard everything had to run on the standard ... 42" diameter... yes it looks funny on anything bigger than a #33 ...but it's the standard. Enter Ives, Flyer, Dorfan everyone designs for the "standard"..... Boucher did their own thing with diameter's up to 80" ..but they had a very very small market ... so don't go there.
By the mid 20's the kids that grew up with 1st generation electric trains wanted more ... but the little loop on the floor just did not cut it anymore ... and the soup cans on wheels had lost their charm .... enter the age of realism .."scale modeling" . Paul Egolf headed the charge on 1/4 " scale O gauge , 1/2" was the domain for live steam ... 1 gauge had pretty much vanished this side the the pond ...but it scaled to 3/8" + - ... and "standard gauge" had no standards in the scale world .... a few choose 3/8" and a few went with 7/16ths .... Paul Egolf bumped his diameters out to 72" ..( yes the original 072 only 10 years before the market leader Lionel ) ...but for real scale the boys laughed at anything less then 96" for 1/4". Standard gauge ..in scale ... now you are up to the 10' + to come close to anything approaching reality .....and that was the breaking point for the big gauges ... death of standard gauge was swift, big man on campus in the 1930-32 range was swept aside by 1934 with O gauge ...which in turn was struggling for second by a the rapid up start of HO by WW2 .
Standard gauge modeler Jack Schaaf began as a kit basher of Ives trains .. but up his skills by 1934 with his brass E6 ..followed by his finest, a Pacific . ... Jack modified Ives transitional Flyer cars .. which are relatively close to 3/8" scale if you extend them ... Jack ran on Gilpatrick's RR in CT... articles found on Popular Science January 1935 ( same issue has Bill Walther's article about his full scale M10,000 ( yes it came out the same time as Lionel's ) 1 /4" ..his first entry into O scale ...leaving his standard gauge layout behind).
Lobaugh ... Rollin known far and wide for his fine O scale ... early some 17/64ths ,,but mostly 1/4" ......and 7 /16ths oh yes standard gauge ... now you have the proper overhang of the cars ... big and meaty ..think O scale kit car on steroids ...these cars built up with hand lettering set you back $30-35.00 each car ...in 1934 that was huge money ... same money bought you a 400E .. no engines listed in the Lobaugh catalogs ..but they have to be out there some where at least a few of them ... where ? ...
Here you have Jack Schaaf's E6 . roughly 3/8" ...pulling a string of Lobaugh freights 7 /16ths ...around a 87" loop ... it's tight !