Enfield threads, many of them, were developed in the 1830s through to the 1860s.
They are "goofy" by modern standards because they don't interchange with what we use today.
Why should they? They were the FIRST standardised, fully-interchangeable system of threads in the world. If anything, the modern stuff should be compliant with THEM.
The system was nailed down by Sir Joseph Whitworth. He later used the Enfield threads as his starting-point when he designed his 55-degree round top/round bottom system of threads which is now called (in the fine threads) British Standard Fine and in the coarse threads, the British Standard Whitworth thread.
Lee-Enfield rifles up to and including Number 1 Mark VI use the Enfield thread system. Threads were changed on the Number 1 Mark VI from Enfield to British Association (BA) and the resulting rifle was called the NUMBER 4 Mark 1. BA is a fine thread on a metric shank; you should be able to get them from any shop specialising in model trains and such.
Number 1 Rifles will have screws with round "cheese" tops whereas the screws on the Number 4 have FLAT tops.
Working on "Enfield" rifles, it really helps to make clear exactly what you have.