As the title says, my question is about how Malfoy got his Hand of Glory. It can't be in the Chamber of Secrets, as Lucius was more eager to sell, than to buy. Plus, he openly disapproved of Draco's choice:

> 
> "I hope my son amounts to more than a thief or a plunderer, Borgin," said Mr Malfoy coldly, and Mr Borgin said quickly, "No offence, sir, no offence meant-"  
> 
>  "Though if his school marks don't pick up," said Mr Malfoy, more coldly still, "that may all he is fit for."  
> 
>  Chamber of Secrets, Chapter 4  
> 
> 
> 

Later, in the next three books, there is no mention of the Hand of Glory (if my memory doesn't deceive me.)
However, in book 6 (Half-Blood Prince), Ron mentions the Hand of Glory and wonders if Draco could have broken it. 

> 
> "Maybe he's broken his Hand of Glory," said Ron vaguely, as he attempted to straighten his broomstick's bent tail twigs. "Remember that shrivelled-up arm Malfoy **had**?".  
> 
>  Half-Blood Prince, Chapter 7
> 
> 
> 

The emphasis, added by me, shows that Ron believed that Malfoy **already had** the Hand of Glory.
So *when did Draco buy the Hand of Glory* and even more importantly, *how does Ron know of it?*

* We can explain away the fact that Ron knew of the Hand of Glory through Harry, but how did he know **for sure for that Malfoy and only Malfoy had purchased it?** There is no mention of this in the other books.

Can someone give a reasonable in-universe explanation for this?