Is this part real LEGO or a knockoff? I bought a LEGO lot off craigslist a few days ago with some sets and some bulk parts. It included some parts that appeared to have been bought in bulk (maybe pick-a-brick?). It also had some random non-lego pieces as we all know is standard to find in these large bulk lots.
Amongst the bulk, I found around 40 of a 1x1x6 support pillar in dark blue color. The part seems somewhat rare and they go for around $5/ea on bricklink, but I'm having a difficult time figuring out if they are real LEGO.
Pictures of said part:




Evidence:

Top stud is hollow which Bricklink says is a normal variant of the
part.
It looks the same as the 3D model of the hollow stud part on Bricklink.
There is no LEGO logo or part number anywhere that I can see.
There is a small seam that runs along the full length of the part on opposite sides.
There is a small number on the outside of the part on the bottom of the rounded section.
The part is the correct dark blue color when compared to other dark blue LEGO pieces.
The part feels like LEGO and has the new LEGO sheen.
I have other parts in my bulk collection that are basically the exact same as these. I would never have questioned that they were real LEGO before I found these.
They were only produced in three sets from 2006/2007: Cafe Corner (4), Piraka Stronghold (6), and The Chum Bucket (4).

Where did he get 40 of them at? Does anyone have parts like this in an official set that you KNOW are real that I can compare them to? Does anyone specifically have one of the three sets this part was found in and can help me do a comparison?
I would obviously like to sell these at some point if they were real, but don't want to sell someone fake LEGO. Thank you for any help!
I've shuffled through my pieces collection and found sadly none in dark blue, but all 17 I've found in either old grey or red have the same attributes you mention:

Top stud is hollow, with an H-shaped cutout
There is no LEGO logo or part number anywhere
There is a small seam that runs along the full length of the part on opposite sides
There is a small number (between 2 and 8) on the outside of the part on the bottom of the rounded section
The part feels like LEGO and has the new LEGO sheen

Single-digit number at the bottom:

H-shaped cutout in the hollow open stud:

Seam running over the opposite sides:

I'm 100% sure these are all genuine LEGO pieces, the red ones from 7419: Dragon Fortress.