With eight sub-references, this is my favorite reference to accumulate, each with its own little characteristics. These watches are so old, and so easy to change, that it is very hard to say if a piece is original. We have instead to satisfy ourselves that it looks original.
In this reference the dial and bezel are a large proportion of the value. If these are missing then be prepared to adjust the value substantially, bearing in mind the suitable parts may never be found.
Case condition on available watches in the market may never be very good. We have to make allowances, and accept a damaged or polished case, or resign ourselves to the idea of never owning one.
The chrono seconds hand was fitted in three executions, the straight hand, shown in the 2998-1 below, the very, very rare lollipop, and the spear seen in the later references below. At no time was the square ended spear fitted. Omega currently offers a service replacement straight hand, but it has a fatter tail and looks wrong. The lollipop hand has been seen on all examples, but without any way of knowing if it is original or not. One surely has to ask, does it matter? (It will, should we ever discover a way of verifying it – but until then, no).
-1 and -2 should have black BASE1000 bezels. These are extremely rare and very often replaced with a DO90 bezel. Recent sale of BASE1000 (as of September 2018) has been rumored to be $20,000. I think even a poor one might reach half that, if true.