I recently came by this rod at a yard sale. I thought it suitable for beach casting for surf perch but after researching it I realize it's more of a collectable than just another pole. All the references are for a 661R model which I believe refers to the Harnell mandrels used for construction. One ad mentioned Salmon/Steelhead which would explain the fighting butt. I'd like to pass this on to someone who will appreciate it for it's collector's value and not just "flip" it.

Harnell wouldn't have written on that block cork with a ball point pen.
I love this stout reel seat, it's the same on my 8' 652.
Though you note my rod has AA+ ring cork instead of the signature block cork Harnell used so often.
And if I was spec'ing a grip shape for a custom rod, it would be this.

the ring cork is 1" wide max, just the way I would spec it.
The block cork on my older 645 and newer 1652 (H-I era "Bronz-Glas" gold-painted blank) is about 0.1" larger diameter, but feels bulkier because of the less-tapered shape.
No rhyme or reason to when or where the differences turned up.
I would guess he used high-grade rings when he couldn't get block.
Also note, the quality of the block cork is lower than the rings - a lot more filler was needed.
All 3 of these rods are jewels and, other than cosmetic differences, the 1652 is delighted with a 6-wt, while the 645 and 652 are definite 7-wts.

Part of the allure is John Harrington continuing hand-rolling his blanks after he (actually partner Runnells) sold Harnell, opening shop again in 1965, and on through the 1990s.
They have a cult following, especially the salt and surf rods on every coast. TX-Mecca Roy's Bait & Tackle sold Harrington blanks as long as he could get them.
His proprietary resin fomulation was strengthened with carbon black (the blanks are black through-thickness), also adding a stiffness contribution from the resin itself.