This is all the information I have. It is from "The Bullion Bar Book" by Jerry Cestkowski.
The obverse from the pics of the 2 bars in the poll look like a Johnson Matthey obverse, as do the 2 pics from Jerry's book, one of which is actually Johnson Matthey.
I have a couple of thoughts about this. The first is perhaps after the initial JM bars were released, Citibank didn't choose to promote JM as the producer and waste that valuable space on the reverse of the bar - the marketing people might have said "Let's put out logo there instead".
They might have even knocked a couple of cents off of the production costs of the bar by using their own die and giving-up the affiliation with JM.
Thanks in advance to everyone who voted.
Gentlemen prefer Engelhard.