He couldn't wear sports clothes while traveling and saving damsels in distress from wild leaping animals, so quite a few covers feature "adventure" or "city" Frank as opposed to "sports" Frank.
Can't tell you much about this particular issue, though I think it takes place in New York, where Frank spent some time working odd jobs before his globe-trotting began. These are street clothes common in the city: a standard men's suit and bowtie. He should have a bowler to go with this, but I forgot to make it. I'll catch up on that another time.