I saw this OMI O scale model (927.1) on eBay yesterday. I thought the slab-side rods, if that’s what these are correctly called, were only applied to the non-streamlined “War Babies”, locomotives 605-610 which OMI also did, I have one. I’ve looked at internet pictures of prototype 613 and the side rods always have a thinner profile look to them than the model I’m referring to on eBay which is pictured below. Comparing the eBay model to the same OMI (927.1) pictured in Dan’s Brass Guide also shows a significant side-rod difference between them. The few prototype photos I’ve been able to find of 613 suggests the one pictured in the Brass Guide is correct and the one currently on eBay is not. It’s possible that N&W did indeed put the thick slab-side rods on 613 but so far I’ve been unable to find any evidence of it. OMI usually did a very good job doing research which complicates the issue further when trying to understand why two OMI models with the same catalog number have very different looking side-rods.