As they used to say in the Bubble Yum commercial: Lemon and lime at the same time!
For years, I've looked over older maps - i.e., pre-1970s - and noticed that US 25/42 actually used two different routings at the same time. US 25/42 used both the Suspension Bridge and the C&O Bridge. They may have even used 3 routes at the same time in Covington: Going north, you may have been able to use Pike or 5th or Main. I think I saw one map where Pike was BUSINESS US 25/42 while 5th was just plain old US 25/42. But I think I once saw one where the 4th/5th pair in Covington was BUSINESS US 25/42. Or maybe it was just 4th, since it might have been two-way then.
I think the split routing on the bridges continued even after US 25/42 added US 127.
Now I've noticed on some Ohio official highway maps from the early 1950s found online that the split routing was actually like a one-way pair. I don't think the bridges themselves were one-way, but northbound US 25/42 used the C&O, while southbound was the Suspension Bridge.
I think I have seen a photo of Pike Street in Covington from the 1970s that had a BUSINESS ROUTE banner but no shield. I know I saw a US 25 cutout on Pike in 1987, but no BUSINESS banner. That was when that was no longer US 25/42.