About Direct reading slides and some...

There is a myth that you can use specific slides for a specific type meter only. This is partially true...
Find out all about the slides here!

BTW, the fastest way to find a proper combination is as follows:
High or Bright slide in: E=(I)x(T) or Take the square root of your film i.e 125 ASA =11, set aperture on your camera accordingly.
Next the reciprocal of the Foot-candle numbers (High Slide in) is your Shutter speed!
Example: reading is 250. Shutterspeed is 1/250th sec. or F16 @ 1.125th sec (sunny 16 rule) Try it next time when you're in a hurry...

These are the slides for the NorWood Director Brockway M-3.
The values are 10 Asa - 1/50 Shutterspeed meant as a direct reading for the film available at the time, the other one is also 10 Asa but for Cine (16 frames per second)
You can see the holes are just a little larger.

Shown here are the "Heliovalves", a very nice thought. The holes are adjustable corresponding with combination letters on the meter. More details can be read at the Heliovalve/SuperDirector page.

First Directors came with a Dark slide, brightslide and later the colormatic slide. The brightslide as it was called these days had also a value of 1/50sec. @ 10ASA
The Darkslide was to underexpose deliberately :-) maybe this was the slide you put in when someone asked to borrow your meter.
More serious, it was used to block all light reaching the cell and check the zero position of the needle.
It was meant to cover the cell when the meter was not in use. (Assuming this would protect the cell from deterioration, lateron it was discovered exposing to light would not harm the cell) Nowadays you need to cup the cell with your hand to block the light, much less accurate I think.

The S series ( Brockway Studio -S and Sekonic Studio -S came with 3 slides covering a range of filmcombinations.
Bright Slide (Nr 1) 10ASA - 1/50. Slide Nr 2 ASA 16 - 1/50 || ASA 32 - 1/100 || ASA 64 1/200
Slide Nr 3 || ASA 50 - 1/60 || ASA 100 - 1/125 || ASA 200 - 1/250
As you probably noticed when you double the ASA value the Shutterspeed goes up factor 1 also, thus many combinations were possible. (A little mental calculation won't hurt)

With the L-28 and up a series of 10 slides were available in a handy wallet. Probably few people knew how to calculate these days and Sekonic had a new gadget to sell. Those with a keen eye can easily see matching slides. Green dot (Same slide different print) || Red dot (Same slide, different print)|| Blue Dot (Same Slide)

Slides can be used on all sekonic models exept the Studio-S

These were for the L-398. The only difference is a slightly smaller ring on top.
Well photographers are gadget freaks so....

Slides can be used on all sekonic models exept the Studio-S

Same story, these are meant for the L-398M.
Note the absence of Film/shutterspeed combinations!
You need the instruction sheet all the time or memorise the numbers.
Slides can be used on all sekonic models exept the Studio-S

High and Bright Slides compared...
From left to right: Colormatic Slide - Director Slide - Type S Slide - Sekonic L28 and up.
The sldes of the elder meters could be used in the newer meters physically. The other way around won't work as the elder meters had rounded corner slots!
There will be a difference of about 1/4 - 1/2 stop though due to the larger center hole.

Case with slides L-28c.
Real leather bookform oblong case with centerfold containing 9 different(sic) slides and one High Slide.
Brass zipper and eyelet for lanyard.

Case with slides L-398.
Much real leather looking bookform case containing 9 different(sic) slides and one High Slide.
Brass zipper and eyelet for lanyard.

Case with slides L-398M.
Less real leather looking bookform case containing 11 different slides and one High Slide.
Eyelet for lanyard.Brass zipper was replaced with push button.
Instead engraved combinations on the slide, there is an instruction sheet as a centerfold.