Qitzur Shulchan Arukh – 188:3-4
One is obligated to guard the deposit in a manner that is better than he would guard his own property. And even if he isn’t all that careful with the guarding of his own items, with a deposit he must be very careful.
The one who receives the deposit is not allowed to deposit the item in the hands [control] of others — even [people] who are more kosher and trustworthy than he is. Except if the depositor is also accustomed to deposit items similar to these with them.