Any time right up until the 1950s I would say. I don't know what you'd call the status of mid-19th century doctors in Britain, for example, but they definitely weren't upper class.
'lower-middle class' is the lower part of the middle class. It's not "lower or middle class". Lower-middle, middle-middle, upper-middle. If it was 'lower or middle', that'd make even less sense - university-educated professionals being part of the working class demographic, at a time when university was an oddity rather than the norm?
