Here you'll find Goodyear welted derbys by Skolyx, Yanko and TLB Mallorca. A derby shoe is recognised by its open lacing, in comparison to an oxford who has a closed lacing. On a derby the tongue is an extension of the so-called vamp which is the widest part of the shoe. If you have a high instep (high ankle) a derby can fit well since the lacing is more flexible.
In general a derby model is a bit less formal than an oxford, but it also depends on colour, decoration, last shape and so on. A black derby without brogueing is a relatively formal shoe.
All shoes from Skolyx, Yanko and TLB Mallorca are made in Spain with a Goodyear welted construction to be easily resoleable and made in high quality full grain leather.