window board treatment

[Abyone]

My Window board in the kitchen is showing signs of wear.
What would be the best treatment approach to make it look better ?
See photos of kitchen window board and Hall window board for comparisson of conditions.
I'd like to leave the finish similar to original where the grain is visible.
I am fairly sure its a hardwood board but not sure what type - could it be teak ?

 

[blup]

Yacht varnish with a polyurethane finish

 

[Abyone]

Thanks - should i sand first - looking to get a sander would orbital or sheet palm be better for this job ?
Also - is varnish better than oil ? Would prefer to use oil if it would be ok.