Answers.Body: <p>I think that this is a production code similar to the seal codes on other sets (e.g. 24R5 for the 24th week of 2015), and you need to add the number from the first dial to the number of the second dial to get a week number, and the Q "dog tag" indicates the production facility this came from. It's missing the production year though, perhaps that was not needed or has been encoded somewhere else on the baseplate.</p>
  
  <p><strong>UPDATE</strong>: The year of production is printed in the center of the single digit dial ("11" in your case) with one digit on each side of the arrow. So your base plate was made in 19Q11, which is the 19th week of 2011. This code seems to be on other LEGO elements as well - for comparison here is a picture of a LEGO Mindstorms EV3 tray from set 45544. It also features a Q, and has a "15" printed in the center of the single digit dial (the full code is 17Q15):</p>
  
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Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2016-04-03T12:33:05.367Z
Answers.Text: Thanks - makes sense. Any clue on when this marking system was started as my plates do not have these marks.
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  <p>I am trying to find out the significance of 3 marks that appear on the back of base plates.</p>
  
  <p>There are 3 circles in a row. The first contains numbers 0-9 in increments of one with a small arrow pointing to a number. The second circle contains numbers  0-50 in increments of 10 with the same kind of arrow. And the third circle contains an icon that looks like a dog tag.</p>
  
Tags: <piece-information>
Title: What are the significance of 3 marks that appear on the back of base plates?
UserDisplayName: Jamie
ThreadText: # What are the significance of 3 marks that appear on the back of base plates?
  
  (Asked by: username_0 on 2016-04-02)
  
  [![enter image description here](https://i.sstatic.net/B8ZBS.jpg)](https://i.sstatic.net/B8ZBS.jpg)
  
  I am trying to find out the significance of 3 marks that appear on the back of base plates.
  
  There are 3 circles in a row. The first contains numbers 0-9 in increments of one with a small arrow pointing to a number. The second circle contains numbers 0-50 in increments of 10 with the same kind of arrow. And the third circle contains an icon that looks like a dog tag.
  
  **Tags:** piece-information
  
  
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  ## 1 answers
  
  ### Answer by username_1 on 2016-04-02. Score: 3 | Accepted answer
  
  I think that this is a production code similar to the seal codes on other sets (e.g. 24R5 for the 24th week of 2015), and you need to add the number from the first dial to the number of the second dial to get a week number, and the Q "dog tag" indicates the production facility this came from. It's missing the production year though, perhaps that was not needed or has been encoded somewhere else on the baseplate.
  
  **UPDATE**: The year of production is printed in the center of the single digit dial ("11" in your case) with one digit on each side of the arrow. So your base plate was made in 19Q11, which is the 19th week of 2011. This code seems to be on other LEGO elements as well - for comparison here is a picture of a LEGO Mindstorms EV3 tray from set 45544. It also features a Q, and has a "15" printed in the center of the single digit dial (the full code is 17Q15):
  
  [![enter image description here](https://i.sstatic.net/VZRDc.jpg)](https://i.sstatic.net/VZRDc.jpg)
  
  > **Comments:**
  > **username_0**: Thanks - makes sense. Any clue on when this marking system was started as my plates do not have these marks.  
  
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