Parts question

[Krkey1]

Phonographs tended to be well built machines ( invariably we all know the individual parts to machines that we curse the original designers for though. Such as anything pot metal) but like everything else they did require repair and replacement parts. So my questions about this are as follows.

 

1.) Original companies invariably made replacement parts for their machines from day one, when did they stop doing this though?

2.) Third party companies made parts too. When did this tend to start and when did this stop?
3.) When do we see the start of parts being made for collector marker?

 

Thanks in advance.