This year's model?

I think I'm happy to report my first mated and laying queen of this year -- at least I hope she is this year's model. Just back from an apiary the colony that was vandalised last winter and that quickly set about making a queen this year now has one from the split I made.

The slight worry is that the colony looks substantially more numerous than it did last week and has suddenly built new comb. Last week it was without a laying queen and so low on stores, I gave it a frame of honey. I'm wondering if a passing swarm has taken up residence -- that happened to one of my colonies a few years ago, but then the increase in numbers was very much more obvious. I'm puzzled. The timing for a mated and laying queen is about right, but the vitality of the colony is suspicious. (It was about to rain so I didn't attempt to seek out the queen to see if she looked new or old.) Maybe the newly queen-right colony attracted bees from the queen-making colony next door.