The breastplate is magical you know that much. Faint aura reading shows that there’s some transmutation enchantment on it but what it does beyond that you don’t know.

The buckler however is entirely mundane, but you vaguely remember this being a dwarven device. A small shield that can turn into a big shield. Effectively, as a buckler you gain +1 AC but you can use your hand holding the buckler freely, allowing the use of two-handed weapons. However there is a means to extend additional protective plates from the buckler to allow it to cover more area and bump up its protective value to a +2, like a normal shield, at the cost of fully occupying your hand like a normal shield. At the moment however it appears that the device is damaged and needs repair. Suitable tool proficiency like smithing or carpentry coul repair it during a long rest, or gratuitous amounts of mending. 

Alternatively you could easily strip away the additional devices, effectively destroying it but retaining a simple buckler in exchange. Beyond the mechanical enchantment the entire shield has no magical abilities or bonuses and appears to be made of mundane steel and wood.