Even the German system seems to be more fallible than it first appears! There is a further problem when trying to cover several companies, as each one will have its own different key dates for introduction/withdrawal of train types or changes in liveries. Before 1948 the only events affecting the appearance of trains across all the companies were the Grouping and WW2.
I can't help thinking that for all the effort put into devising and explaining the era system it would be far easier for everyone if the catalogue/website said something like "This locomotive was in this general configuration and livery between 1956 and 1964, as were others of the same type between 1955 and 1968". This would convey more information in a clearer manner in about the same amount of space! The supplier almost certainly knows the dates from researching the prototype, and if exact dates are uncertain it would be OK to give an approximate date.
I can't help thinking that for all the effort put into devising and explaining the era system it would be far easier for everyone if the catalogue/website said something like "This locomotive was in this general configuration and livery between 1956 and 1964, as were others of the same type between 1955 and 1968". This would convey more information in a clearer manner in about the same amount of space! The supplier almost certainly knows the dates from researching the prototype, and if exact dates are uncertain it would be OK to give an approximate date.
