Some variants of the Reslo RV ribbon microphone

These three microphones have near-identical external appearance, but the internal workings changed over time.
This early example has two larger magnets instead of the three found on later models.
The pole pieces have 4BA studs to mount the ribbon carrier.
A central stud had foam glued to the top to support the assembly.
The ribbon carrier is a simple stamping of SRBP.
Some of the ribbon clamp parts.
The 10202 50 ohm output transformer.
I have extended the ground connection to the upper body.
The RV mics usually had the spare pin of the connector grounded.
Double mesh basket.
A part of the original ribbon.
Carrier ready for insertion of new ribbon.
Th enew ribbon is lighter than the original, so I have added a texture to it in addition to the stepped corrugations.
Ribbon carrier replaced.
Mesh cover.
This second example is slightly later.
The ribbon carrier is still an SRBP stampling.
There are a lot more foam blocks in this one and it has the usual three magnets.
Contains a lot of brown dust.
And an unusual transformer with no markings.
Not sure if this is a Reslo ribbon.
This third example is back to the familiar 10202 transformer.
And has the black moulded ribbon carrier.
The ribbon seems original but the mesh is the wrong way round.
A couple of frequency-response plots sent to me by David Pinnegar. This is from the front.
And this is from the back. I assume the differences must come from the asymmetric stucture.