I bought this plant about four years ago with the name Pelargonium burtoniae. It was not in flower, and I bought it because I did not have this plant in my collection and not heard of it.
When I checked in Diana Miller's Guide to Species I found that P. burtoniae was described and named in 1927 from a plant found by a Mrs Burton in a garden in eastern Cape Province. However, it is identical to the plant grown in Europe as P. stenopetalum for 200 years. I changed the label to P. stenopetalum.
The flowers of P. stenopetalum are quite distinct as you can see from my photographs. They are a very bright pink, with very thin spidery petals and are easily spotted in the greenhouse. The leaves are waxy, pale green with a very faint zone. It is easy to take cuttings of P. stenopetalum and I treat it as a normal zonal, except I grow it in a John Innes No. 2 compost with added grit for extra drainage. It does tend to sprawl a bit.