determening approximate age of vintage Duplo bricks

[Duplotang]

I have a lot of old duplo bricks and want to figure out their approximate age since I'm a bit worried that old duplo bricks might contain unsafe levels of Cadmium after reading reports like this https://tamararubin.com/2019/05/vintage-1970s-legos-test-positive-for-a-high-level-of-a-known-carcinogen-how-can-i-tell-if-my-legos-are-safe/

I have not found any site explaining how to determine the approximate age of DUPLO bricks (some discuss regular lego but not duplo), or just if they are older than ~1990? (when Lego supposedly switch to Cadmium free plastic colorants).

Any tips on determining the approximate age? I see some old bricks have the ©LEGO group logo on the back, some says LEGO A/S, some says just ©LEGO and some has no text at all. Also there are several other differences on the back side of the bricks (see images at link at bottom) but I don't know if that can be use for figuring out the age? For reference the yellow brick is a new brick and the other are somewhat old but if they are from the 70s, 80s or 90s I have no idea.

 

Note, this was also asked at https://bricks.stackexchange.com/questions/18852/determining-the-approximate-age-of-old-duplo-bricks but I didn't get any replies thus a repost here.

Edited October 27, 2024 by Duplotang

[JopieK]

You could test for cadmium of course?!

See e.g. http://www.home-health-chemistry.com/Cadmium-Test.html

[Duplotang]

That's an option I haven't even considered... but yeah possibly.

If there is a way to figure out the approximate age I would prefer that though.

[Duplotang]

Does anyone know at least when they started adding "(c) LEGO Group" to the bottom of the bricks? Or when Lego group was founded?

The best page for information on this is https://www.leggodt.nl/items/lego/date-logos.php but this page does not go into this either.

[Murdoch17]

3 hours ago, Duplotang said:

Does anyone know at least when they started adding "(c) LEGO Group" to the bottom of the bricks? Or when Lego group was founded?

The best page for information on this is https://www.leggodt.nl/items/lego/date-logos.php but this page does not go into this either.

Lego was founded in the 1930s. Don't know for sure about the copywrite part of your question, but I would assume that they would have started doing that around the late 50's (when the 2x4 brick was patented) to protect the brick from copycats.

[Stereo]

7 hours ago, Duplotang said:

Does anyone know at least when they started adding "(c) LEGO Group" to the bottom of the bricks? Or when Lego group was founded?

The best page for information on this is https://www.leggodt.nl/items/lego/date-logos.php but this page does not go into this either.

I have some '80s Duplo and there are some pretty noticeable changes to the underside of the bricks, one kind (I believe older, maybe 1985) has no dimple on the top of the brick, and no rough texture on the underside.

DUPLO(R) LEGO A/S Interlego AG  20 5

the other (nearer 1990) has a ~6mm dimple on the top for the injection point, and a rough texture on the underside.

3437 33-4

(both are 2x2 bricks; 20 5 and 33-4 would be mold identifiers)

I'm just basing the guess on the fonts used, the one I'm considering 'older' looks like they got hand-stamped into the mold, the 'newer' one looks machine placed.  I know my newest Duplo is from around 1990-1991, the older is from my 5 year older cousins so probably not older than 1982 or so.

 

I didn't see your photos when I initially wrote my reply; these are like your blue and yellow ones for the most part, though not identical as there's no "LEGO Group" on the one with 3437 on it.

Edited November 16, 2024 by Stereo