Lesson 1, Section G provides 'pen / pan' as an example of 'D' (different), and 'man / men' also has different middle sounds (/æ/ and /e/ respectively). 'Pen / ten' and 'bag / mat' have same middle sounds.
Class 3 › English Text Book › Chapter 4: Let's Play with Sounds and Numbers › Topic: Saying the middle sounds /æ/ and /e/
Aligned to the NCTB national curriculum.