Logo: Modern logo.
Material: ABS (solid), PP (transparent)
Inner ribs: On the long and short sides. Visible as a frosted line in transparent bricks.
Inner tubes: with flat bottom
Flowrib / center line inside top surface: Yes.
Mold pip: on the short side.
Mold numbers: 343 to 350.
The numbers 343, 344 and 345 are in the smaller font version.
Intellectual property protection: None.
Design ID (3001): None
Colors known: Regular production bricks made in this mold are known to exist in Transparent (trans-clear) only.
Other colors have been found in lots that also contain known Bayer bricks. Colors found include Transparent Red and several non-production colors.
[Original post and comments on Flickr.]