I'll try to explain my logic:

Firstly, we know that an SCM tradehold is 7 days.

We also know that the Safe left DX's inventory either the 21st or 22nd of March.

We also know it appeared in Mauser's inventory some time between March 22nd and March 28th.

so sometime in that 7 day span, the item was purchased. (22, 23, 24, 25, 26, 27, or 28 of March)

Now, if we extend the compare link to the next day:

https://backpack.tf/profiles/76561197993239135#!/compare/1584835200/1585440000

we can see that the item is still not tradable, so it cannot have been sold on the 22nd, also ruling out any day before the 22nd.

if we extend it to the next available day: (31st of march)

https://backpack.tf/profiles/76561197993239135#!/compare/1584835200/1585612800

we can see it becomes tradable.

therefore, the sale MUST have happened 7 days before the 31 or 30th of march.

therefore, the sale must have happened on either the 24 or 25 of March.

since there is only one sale on the 25th of March, and no sales on the 24th, that must be the sale.

If there is anything that I have missed or not thought about, please do correct me!

If you couyld also double check the sale and key price, for some reason every value on Steam for me has changed by a small yet noticeable amount, and I want to see if I messed up real bad or if it's a steam issue.