I agree with Ben's assessment and have sent you a scan of a builders photo of one of these cars built by Standard Steel, which I got from Keith Retterer.
Regarding the side post gussett, it's been my observation that these often varied in cars produced to the same design by different manufacturers. I have been unable to account for the differences.
Regarding the heavier top chord/side rail, many early cars had their top chord/side rails reinforced with heavier angle during their lives. Good examples include the B&O's N-10 and the PRR's H21 cited by Ben.
