In the UK standardisation to AC and commenced from 1926 but it took time, this chart
shows the variety of voltages in London in 1910. (Please excuse the writing it is a completely unedited text - rather dreary 'notes' in places too.) The US must of started standardising around the same time. But a lot of small companies carried on supplying odd voltages for time after that date. There is a huge crossover period of 20 years so really the worse time to use such information for dating.
The carving of the wood would not be to expensive as cheap labour was still the norm until the 1950s. Such work was probably easily available until then. Biggest factor in dating fittings are the construction techniques and brass colouring and finishing. Other metals used help too. But bear in mind that it was not unheard of for an owner to have a vase converted privately and these could afford the best work. Other lighting companies bought in the glass or providing a service/parts to glass companies. Matching to the vase being fitted was obviously the way it was done.
See the bottom row here http://www.ysartglass.com/Moncat/PageLighting.htm
the Monart FL23 was done by a London company for Liberty's. The one on the right FL25 I suspect to be American made and the conversion, it is a vase, done in the US. I have also had a vase converted to a lamp FL13 on the same page, where the wood base was painted to match the glass. The Moncrieff sourced fittings were of another quality altogether.
The fittings themselves are relatively easy to date as the development of technology was fairly consistent in thess things and ten years would be the biggest error in such a date.
In this case, the base could have been commissioned by the factory and in that case appear in a catalogue with it. Finding the vase without the base in a catalogue would not help as far as the base is concerned. Who knows, when I get to them I may even have such things in a lighting company catalogue. I have quite a few....