This is not the first time Cook has stepped in while Steve Jobs dealt with a serious medical condition.

Cook ran the shop for a month in 2004 while Jobs recovered from surgery that removed a malignant tumor from his pancreas (see here). The stock fell then too — down 2.3% on Aug. 2, 2004, the day after Apple announced the news — a loss that widened to nearly 8% by week’s end.

But by Sept. 1, 2004 the stock had not only recovered, but gained 10.9% on its July 30 price — closing at what now seems an impossibly low $35.86.

Some of that bump may be attributed to investor relief that Jobs was due back at the helm. But whether or not Jobs returns from his latest medical leave, the fact is that Tim Cook has been running day-to-day operations at Apple for some time, as Adam Lashinsky’s long profile in Fortune makes clear. (See The genius behind Steve.)

In July 2004, two weeks before Jobs’ operation, Apple reported earnings of $61 million on sales of $2.014 billion and was holding just under $5 billion in cash.

In its last quarterly statement, Apple reported earnings of $1.14 billion on sales of $7.9 billion, with nearly $25 billion in cash.

In other words, it’s the same company, only four or five times bigger.