I gather that one of the boys spotted him, though he meant to do it quietly.

The fact that he didn't announce his name is rather suggestive.

You can read the message." He took it from his pocket and handed it to Stirling, who wrinkled his brows.
"Well," he observed, "what Van Staten says goes.

Very few of the big concerns would hesitate to purchase when he was satisfied with the thing.

That storekeeper seems quite a smart man.