Well thank you, Saambou. It's great for the lineages to re-connect, and just watching this has really been a treat!
This set is called the 滚躺双刀/
Gwan Tong Seung Do/ "Rolling Double Knives".
Now that I think back (conversation, maybe 20 years ago), the name of the set my Sigung was said to have played may well have been "
Gwan Tong Seung Do", and when I said, "Huh?" I was then explained it meant "rolling, rolling on the ground". From that, I may have thought that I had heard
Dei Tong/ "Earth Court", (another name for floor technique), and simply left it at that. When I asked what happened to the set, I was told, "
Buk Pai" (Northern),
"very long time no practice". Therefore, I didn't pay it any further attention, until just now.
As we can see, the manner in which the knives are held in the above-shown
Gwan Tong Seung Do (at both the beginning and the ending salutations), most certainly bear testimony to Northern origins.
Gwan Tong Seung Do/ "Rolling Double Knives" contains so much in common with my Sigung's
Mui Fa Seung Lung Do/ "Plum Blossom Double Dragon Knives", that I would go so far as to say it is likely the same, just that the salutations were changed, the
Dei Fa/ "Ground Flower" removed, and other adjustments made, similar to other knives that my Sigung has adapted (the
Pek Gwa Daan Do and
Ji Faai Daan Do/ "Commander's Knife", for two main examples).
Once the
Dei Fa/ "Ground Flower" was edited, it could no longer be called
Gwan Tong Seung Do, therefore,
Mui Fa Seung Lung Do/ "Plum Blossom Double Dragon Knives" would be the more appropriate.
Well, this has been conjecture on my part, but it would certainly connect a few loose ends, and because such adaptation and conversion are a hallmark of my Sigung, frankly, it would not surprise me in the least.
The way my Sigung would explain it to us, the
Mui Fa Seung Lung Do that we see today, was a collaboration between GM Lau Jaam, and GM Lam Cho himself.

Best,
Michael