1. Does your friend already know how to use a sextant?
2. If the answer is yes, you better ask him wether he would like a US$ 500 or plus metal sextant, or a US$ 150/200 plastic one. You may also find US$ 1500/2000 metal sextant. If he knows how to drive this thing, he probably has some predefined likes, such as weight, type o mirror, light, etc, and you would like to know exactly what he wants. (Unless you are able to change it at the shop)
3. If the answer is no, and he is planning to take a course sometime, since the offshore passage is scheduled in a couple of years, you''d rather evaluate if a sextant is the correct present for Xmas. If you spend US$ 1000 in a good sextant, you will probably find yourself asking when this guy will start learning to work out this ******* thing.
In this case I will probably consider other present.
However, let me tell you that the sizes in inches of almost all the sextants, are the same. The difference is the weight, depending upon they being plastic or metal.(the latter, expensivier)
At the very end, if you don''t have any budget restriction, you will go for a metal one.
Best regards, and Happy Holidays