Hi Mijkarf, I did a quick search up the ladder but couldn't find a clue word. They are the Gold Box grey plate gold pin tubes, right? Harsh? this what "Joe" had to say:
"Sylvania Gold Brand grey pl ate gold pin - OK, this is the
legend. When people talk wantonly about the famous Sylvania
Gold Brand 5751 gold pins this is the tube they are referring
to. Does it measure up to the hype? Well by and large, yes. To
my ears it is the the 2nd or 3rd best 5751 ranking up there
with the Sylvania & GE black plates. Its strength is its
midrange, but it may also be its weakness. The mids here are
full, lush, tangible and maybe (just maybe) a trifle
overblown. Occasionally i find the lush full vocals obscure
just a bit of detail and reduce transparency slightly, but the
mids are so lush I could understand how you might not care.
The tube also has a measure of life and vibrancy, similar to
the Sylvania's black plates and it also has a bit of the
forwardness that's seems to be endemic to Sylvanias in the
5751 family. I've lived with this tube enough to know I could
use it quite happily, though that would be in the context of a
fairly neutral system where its own colorations would not go
over the top. If your rig is already warm, smooth, lush and a
bit lacking in detail this guy could turn things just a touch
syrupy. But given the sound of a lot of cd based systems he
could be just the ticket... Availability on this guy is
limited. His reputation has made him a rare, if not
outrageously expensive beast (usually $30 - $40 a tube) and he
is long lived"
"Sylvania Gold Brand grey pl ate gold pin - OK, this is the
legend. When people talk wantonly about the famous Sylvania
Gold Brand 5751 gold pins this is the tube they are referring
to. Does it measure up to the hype? Well by and large, yes. To
my ears it is the the 2nd or 3rd best 5751 ranking up there
with the Sylvania & GE black plates. Its strength is its
midrange, but it may also be its weakness. The mids here are
full, lush, tangible and maybe (just maybe) a trifle
overblown. Occasionally i find the lush full vocals obscure
just a bit of detail and reduce transparency slightly, but the
mids are so lush I could understand how you might not care.
The tube also has a measure of life and vibrancy, similar to
the Sylvania's black plates and it also has a bit of the
forwardness that's seems to be endemic to Sylvanias in the
5751 family. I've lived with this tube enough to know I could
use it quite happily, though that would be in the context of a
fairly neutral system where its own colorations would not go
over the top. If your rig is already warm, smooth, lush and a
bit lacking in detail this guy could turn things just a touch
syrupy. But given the sound of a lot of cd based systems he
could be just the ticket... Availability on this guy is
limited. His reputation has made him a rare, if not
outrageously expensive beast (usually $30 - $40 a tube) and he
is long lived"