John, I think you're confusing a couple of shutters.
Originally Posted by jnanian
The Polaroid MP-4 shutter (the face plate says just that, Polaroid MP-4) has a shutter release lever, one cable release socket and a "shutter open" lever (also called press focus lever) like regular cock-and-shoot Copal #1s. These shutters have no diaphragms so are useless for most purposes. I have one in front of me, I'm not making this up.
Prontor Press #1 shutters for the Polaroid MP-3 system have no shutter release lever and two cable release sockets, one for tripping the shutter, the other for opening it for focusing. Some have diaphragms, others, e.g., as supplied for the 35/4 Eurygon, don't. This is from memory, I'm still not making it up.
The Copal Polaroid shutter your (mine, too) 127/4.7 Tominon is in is a #1 press shutter, has one cable release socket and no provision (besides using the shutter's "T" speed setting) for opening it for focusing. My 127/4.7 Tominon is in my camera bag but I have one of the shutters with a 210/5.6 Fujinon in front of me.
Copal Polaroids as sold with Tominon lenses in them (not front-mounted on) them aren't to the Compur/Copal/Prontor/Seiko #1 shutter standard. The standard tube length is 20.00 mm, Copal Polaroids have 22.00 mm tubes. In addition, they have limited maximum openings. The one I put my 210 Fuji in won't give full aperture with that lens. But they're cheap and lenses for #1 that are mounted in them still pass light and form images so their users are happy.
One of my friends wrote a ray-tracing program and uses it to estimate lenses' performance. Eric Beltrando, visit his site www.dioptrique.info . When I discovered that my cheap Copal Polaroid shutter was too long and asked him what effect the extra 2 mm would have on a 6/4 plasmat's performance, he told me that in this class of lens performance is relatively insensitive to cell spacing and that the ill effects are far off axis. It was safe for me to use these lenses on my little 2x3 Graphics. Dagor types' performance is much more sensitive to cell spacing, so I shouldn't use my Beryls or my one dagor type G-Claron on Copal Polaroid shutters.