I recently was able to get a 1978-79 Morley PFL flanger, and I can tell you, these things may be the best modulation pedal ever made...once you get them adjusted correctly.
I figure to lead off with the good stuff, an inside shot:

Thankfully, the SAD1024 was intact and working perfectly. Huge sigh of relief when I opened it up!
Here's the outside. It doesn't look too bad for being 40+ years old:

Now the part that can be scary at first. When I first powered it up, it worked, but it didn't sound good at all. It was nothing like the one Andy Martin demos in his youtube video. Mine didn't do any kind of oscillation. The flanging was shallow and lifeless.
I'm sure you noticed all the trimpots all over this thing. That's the key. Somebody had really messed this thing up at some point. The 100k and 25k pots in the upper left control the low and high limits respectively. The 100k pot was adjusted so there was no bottom end in the sound. Once I adjusted that...boom, there was that thick/syrupy/watery flange that really only an SAD1024 can produce. I've never owned an SAD1024-based pedal, but there is definitely some special mojo in that chip. The 25k "high limit" pot can be adjusted to taste, but that 100k "low limit" pot is critical to the overall sound. The other thing to mention here:
this thing is quiet! How is that possible? The SAD1024 is supposed to be a noisy beast. Credit Ray Lubow for designing an excellent circuit here. It's more quiet than any BBD-based effect I've ever used. Very, very minimal hiss and absolutely zero clock noise of any kind even at the most extreme settings. And no 60-cycle hum despite the fact there are TWO AC transformers in there. Amazing design.
Next was the 25k pot located pretty much dead center in the board. That controls the harmonic emphasis (feedback). It was adjusted way too low, so no oscillation was possible even at the max setting on the outside control. A bit of clockwise turning and I was right in that crazy oscillation territory that can then be controlled with the foot control. It's great.
Some of the sounds these can create are not for everyone. The physical size of this beast certainly does you no favors on pedalboard space either. But if you like being able to push modulation to it's limits with that classic 70's flanger sound, there is hardly another pedal-format flanger that can beat these.