Canon EF-M body + M39 lens
COMPATIBLE IN THEORY MF MA
The flange focal depth would allow conversion, but...
There was an item titled M/L39 which was actually an alternate name for the L39 with a rangefinder. Just to make life more complicated, the Soviets used the M39 designation not only for a rangefinder, but an SLR system as well, which is a 39mm wide threaded connector with a flange focal depth of 45.2mm. This is very similar to the M42 and several early Helios optics (for example the Helios 44 2/58) were available both in M42 and M39 (SLR) version.
Nowadays most misunderstandings besides the names com from the fact that there are M39-M42 adapters sold on eBay, which are actually rings made of very thin material and threaded on their in- and outside. Screwing them on a 39mm thread they convert it to 42 mm wide allowing to fix an M42 lens on an M39 mount. However, you might have noticed that the flange focal depth of the M39 is less than of the M42 (45.2mm vs. 45.46mm, 0.26mm difference).
The difference might seem to be marginal, but anyone who is familiar with manual lenses and had faced the issue with focusing on distant objects will know this minusucule difference will be decisive when very trying to sharpen a distant subject's image.
A proper EOS-M - M39 adapter cannot be found on the Internet (searching for M39 will get results only for L39 rangefinder adapter). A possible solution for this problem might be ,to buy a simple EOS-M - M42 adapter and an M39-M42 ring, remove the M4/3 adapter's M42 thread fixed by the three bolts and very carefully sand off 0.26mm (or slightly more), bolt in the M39-M42 adapter and will sit 0.26mm deeper, which means we'll get a fully functioning lens. Ideal for DIY types.
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