Morris Minor Owners Club

Perusing the ESM website I see two master cylinders.

One described as 'original spec' is £88.50 ex VAT
https://www.morrisminorspares.com/brake ... ec-p829360

The other, described as 'pattern type' is £39.50 ex VAT
https://www.morrisminorspares.com/brake ... s-p1238439

What do the descriptions mean for me bearing in mind that I have a late car and am happy with the performance of the original unmodified braking system?

Original means just that. It is an original manufacture. A pattern means it's a copy where the dimensions, materials and finish from the original may or may not be used to manufacture a replacement (a copy). There is much debate regarding pattern parts and many examples of poor quality, dimensions, materials and finish. That said there are also acceptable pattern parts. As original parts become more difficult to source patterns may be the only alternative. But, be careful as original spec is a loose term and may or may not be original manufacture.

Read the two respective descriptions.
Clearly explained.
Summarised as 'original spec' is exactly the same, can be serviced by replacing seals.
Howver 'pattern' will operate in the same manner (fit/form/function) but for example cannot be serviced by replacing any seals. It may not be designed with exactly the same internal components.

Also check out
https://board.mmoc.org.uk/viewtopic.php?t=76653

Thanks for the response.

It would appear that paying more for 'original spec' may or may not guarantee a faultless component but at least improves one's chances...