How to tell a primary source from a later account (for students)

The most useful history skill is asking "how do we know?" A quick way to teach it:

1. Made at the time: a letter, a coin, a photo, an inscription.

2. Written later: a history book, a memoir decades on.

3. Scientific finding: what tests on bones, soil or ice show.

4. Modern reconstruction: a painting or model of what it might have looked like.

5. Ask of each: who made it, when, and why?

PastRush turns history into investigations with exhibits labelled exactly this way: made at the time, written later, scientific finding or modern reconstruction. Six of 12 investigations are free, including the Rosetta Stone, Pompeii and Ötzi the Iceman. A 3D globe has a Time River back to Pangaea, and Class mode works on shared devices. No account, no ads.

What's a history "fact" you later found out was a reconstruction?