These bricks are probably Minitalia test bricks made by LEGO in Denmark. These bricks have the Minitalia version of the split tubes, but unlike Minitalia they have hollow studs. The Minitalia bricks had a recessed stud (like technic bricks or modern minifigure heads) and no hole on the inside.
Logo: Modern logo.
Material: White same as Minitalia? The rest are ABS.
Wall type: Thin with vertical ridges, without cross-support
Inner ribs: none
Inner tubes: with split tubes (parallel to short side). The split is narrow on bricks G, H, J and wide on the other bricks.
Flowrib / center line inside top surface: No
Mold pip: on the stud with the letter.
Mold position numbers:
Letters F, G, H, J, K, L, M, N on one stud, normal LEGO logo on the other studs.
- F, H, K, L, M, N below left tube
- R (on G brick) and S (on J brick) above left tube
- The different ranges of letters suggest that this mold might have reused parts of an older mold.
Intellectual property protection: Pat. pend. on bricks R and S, not on the others.
Colors known: Blue, Black, Light Gray and Red, White. (Minitalia was also made in yellow and green. I wonder if we will find those…)
- Letters on the studs.
- Minitalia version of the split tubes
- Are these really Minitalia test bricks?
- Like so many of the odd bricks… why were these made?
[Original post and comments on Flickr.]
See also this post by Maxx, with the following image: