And why I'm talking more of a replica
In the world of effect pedals, the term "clone" is commonly used. Such pedal is a clone of the Jumbo Tonebender, such other is a clone of the mythical Interfax Harmonic Percolator, etc.
Even if I sometimes talk about "clones" or "copies", I prefer to use the word "replica".
The issue with the word "clone" is that it makes us think of an exact copy. However, it is impossible to make an exact copy of a pedal that was first created 40 or 50 years ago.
1) The pedals of this glorious era that have survived to the present day have electronic components that have deteriorated over time. Or they have been repaired with other components. So these pedals have a different sound from the one they had decades ago.
2) Components from the 1960s or 1970s are no longer produced in almost all cases. There are often modern equivalents, but they will never have exactly the same characteristics as the old ones.
3) Manufacturers at the time sometimes used components whose value varied greatly from one batch to another, or even within the same batch.
4) Quality controls were less drastic than today. Soldering resistors of 10k instead of 1k by mistake could easily go unnoticed.
For all the above reasons, it is impossible to make a clone, an exact and perfect copy of a pedal that is over 40 years old. We have to deal with the most recent components. Deal with what we know about these old pedals. And sometimes imagine the missing information. That's why I prefer to use the term replica.