I see a lot of topics on these reels. I was curious and searched but did not find an answer. How many series were there? I see system 2, 4, etc. What is the difference among the various numerical series, i.e. a similar model in each series? I kind of remember when SA introduced these but I've never used one.

The first was a reel made by Daiwa.It was a decent reel.Actually before that there was a reel that was actually a Hardy Marquis.After the Daiwa there was the Sysem 2.These were fairly rugged reels and went up to 9 or 10 wt. lines.These were made by Leeda which later became British Fly Reel.Then came the System 2L which were lighter reels but were excellent with a disc drag which the System 2 also had.There was the System 2LC which had a click drag.There were also some later click drag reels.After the System 2L there was the System 2M which was in between the 2 and the 2Ls.There was also a System 6 which was a high end that was around $600.00 back around the 90s.There may even be others but I cant remember.

we're here again - there's a difference between System numeral and System One Two, etc. - they have two different meanings

actually, it's easy to sort out of you read

System 4, 5, 6, 7, 8, 9, 10, 11 - matching rods and Hardy Marquis reels numbered by line weight
System G4, etc - same idea in graphite
System One, System Two, System Two L, M - new series of reels with each model numbered for correct line weight match.
Maybe just turn this thing on.

Thank you, gentlemen.

System is a trademark for Scientific Anglers, a call on their disciplined, empirical approach to tackle and fishing.
And especially in the glass rod series, hard to argue against perfection.

Probably some of the various iterations can be linked in time to the trademark reassignments, which may reflect changes in management, manufacturing, and retailing emphasis.
Here's more than enough info for a search at the US Patent/Trademark office for a lot more research than I want to do.

Word Mark
SYSTEM

Goods and Services
IC 016 018 020 022 025 028. US 022. G & S: FLY FISHING EQUIPMENT, SPECIFICALLY, [ RODS, ] REELS[, AND LINES]. FIRST USE: 19680828. FIRST USE IN COMMERCE: 19680828
Mark Drawing Code
(1) TYPED DRAWING
Serial Number
72318832
Filing Date
February 10, 1969
Current Basis
1A
Original Filing Basis
1A
Registration Number
0884969
Registration Date
January 27, 1970
Owner
(REGISTRANT) SCIENTIFIC ANGLERS, INC. CORPORATION MICHIGAN 1012 JEFFERSON AVE. MIDLAND MICHIGAN 48640
(LAST LISTED OWNER) Scientific Anglers LLC LIMITED LIABILITY COMPANY MICHIGAN 178 CONSERVATION WAY SUNDERLAND VERMONT 052504465


Very interesting to me--and makes perfect sense, that us old timers think first of the Hardy-based reels. I still remember a guy showing me one he was quite proud of on the Battenkill in the early 1970s. So that's almost 50 years ago, and now even the "new" System Number stuff goes way back but would be thought of first by "newer" anglers.

As I mentioned above, more than a decade is not too shabby for a product (the Marquis-based reels) especially in the era of "planned obsolescence" and rapid economic and technical change, the "system" trademark having begun in about 1970. In terms of continuity, it may look less coherent in retrospect than it was. Bulldog sorted it out pretty efficiently. System "Numeral" as in jgstar's great pics. Next, at the time, System One (word) would have distinguished from the "old" and signaled a "new" product, the more so because there were no System 1, System 2, or System 3 reels. Later, System Two would have been easily recognized as distinct from One.

I’ve a number of the Daiwa SF706 reels. I think one of the biggest appeals to me is that if a dual pawl such as these gets gritted up on a local stream, all I have to do is remove the spool, rinse the frame and spool in the river, reassemble and go on fishing. Some of finer tolerance, cork/carbon/whatever drag system reels don’t do that.

That appears to be something they changed along the way - may have coincided with the move to Korea.
But one thing for certain, the latter are more contemporary reels.

I fished with Billy Trimble on a couple of treks along the CO/NM border, when he was a trout wizard and wouldn't even sit through a conversation about coast fly fishing. (Now he's one of the top TX coast fly fishing guides and speakers)
When his Marryat locked up on a San Juan fish, he threw it from the top of a cliff into Simon Canyon.
After that, he fished nothing but System One reels.

exactly - and the new System 4 looks like the wheels that keeps spinning after the SUV stops.

I think I have a System 1 reel around here somewhere that says Made in China on a decal on the reel foot. After Korea? If manufacturing costs continue to rise, one could expect reel manufacturing to move to Vietnam or India--as other things have.