Don't think I've ever seen a prototype piece of rolling stock with X2F couplers!
And, of course, because of the above reasons, the manufacturers no longer produce items with the old coupler.
So the knuckle couplers maintain all the "pros" minus the "cons."
Actually the cons remains for many including the #5 and other sizes(20s,30s and 40s) being more to S Scale then HO...We average mortals accept the knuckle spring where many of todays advance modelers are turning to the Sargent coupler due to them being more realistic looking...However,not to be out done many of the average and above average modelers are turning to the scale couplers sizes as the new de facto standard.
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