I am nothing if not obsessive when I am interested in something, so I will add some more info regarding the Ener-G and Ener-G II model# number problems here. I've been working on this for a while now, so I don't know if any posts have been made after my last one I made in this thread...
1740 / 1740BLK / 1740BLKST
The 1740 had "Handle is textured gray G-10 w/ black Trac-Tec inserts with Sandvik 13C26 stainless-steel blade". Here is a link to this knife from BladeHQ, which shows model# 1740 on blade:
http://www.bladehq.com/item--Kershaw-ENERG-Manual--4713.
Here is a link to a 1740BLK, listed as an Ener-GY (The "GY" designation is new to me) from BladeHQ which has black G-10 handles and a Sandvik 14C28N satin blade (model# cannot be seen on blade in picture):
http://www.bladehq.com/item--1740BLK-Kershaw-ENERGY--4259.
Here is a link to a 1740BLKST from BladeHQ, which has a black serrated blade, as would be expected (model# visible on blade):
http://www.bladehq.com/item--1740BLK-Kershaw-ENERGY--4259.
The 1740BLK with the satin blade that I received has a date on the blade of "Feb 09".
I have found a customer's pictures of a 1740BLK with a satin blade on Amazon. That has no date on the blade. The poster of this picture made the following comments, "Show pertinent information like the designer, model no. and country of manufacture. Wish they included the blade steel. My 1st generation Ener-G (or NRG), with the green and black handle, had 13C26N steel. This 2nd gen. has the 14C28N steel by Sandvik. An interesting note, the 1st gen. included the manufacturing month and year on the ricasso, which was not included in the 2nd generation. Mine had "SEP 07" and "This is the 2nd generation Ener-G. This is the correct rendition of the 1740BLK knife, which I received. Its 14C28N blade is not Tungsten-DLC coated, as the original photo might lead you to believe. Instead, it has a beautiful satin finish. From what I know, the bigger 1745BLK has the Tu-DLC coat, but this 1740BLK does not, even though they have the same -BLK suffix.". So, the 1740BLK with a satin blade has been confirmed to exist with a "Feb 09" date and with no date.
I have found one picture of a 1740BLK with a black blade where I can see that date side of the blade, but the resolution of the photo is low and that I believe the blade is dated May 06 or May 08.
1745 / 1745BLK / 1745BLKST
I have found a picture of the 1745 with the original two color handle and satin blade with a blade date of Jun 06.
I have found a picture of a 1745BLK with black handles and a satin blade which is dated Feb 09.
Here is a link to a 1745BLK with a black blade on BladeHQ (no date visible):
http://www.bladehq.com/item--Kershaw-ENER-G2-Flipper-Knife-3--8517.
Here is a link to a 1745BLKST with a black serrated blade on BladeHQ (no date visible):
http://www.bladehq.com/item--Kershaw-Knives-ENERG2--4714
I can find a picture of a 1745BLKS black serrated blade showing a date of May 08.
I can find a picture of a 1745BLK black blade with no date on the blade.
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My findings in these sort of issues always SEEMS to indicate by the dating that items that were originally produced with black blades, were produced with satin blades at later dates with no change to the model# (although, I am not sure when Kershaw stopped dating blades and some undated black blades exist when their are dated satin examples.)
(By the way, if Kershaw is looking to hire a librarian/historian, I really like Oregon!

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