Cracked glass/ Mcintosh

Either it's been mishandled during shipping or after shipping.

I don't think you're liable personally, but as an incentive, you can offer buyer to help in insurance claim.

You can also say that it's been quite a while after it was shipped and who knows or who should really know what was happening with amp between date of delivery and over 10 days after, but instead you let insurance company say same thing and politely remove your personal liability.

P.S. I'm experienced retailer and sell vinyl records online and off the store front and dealing with cases like that almost on daily bases.

I'll bet anything that he did it himself while he was handling it after unpacking. He may have turned it on it's face, or done something else accidentally. It is not hard to do. A repair person experienced with Mac once did it to my amp. Also, if it arrived that way, he would have informed you right away.
If you want to assist, as the other poster suggested, you can call the shipper on his behalf, but they are going to be very suspect of such a late claim, and I wouln't get deeply involved. You certainly don't owe him any compensation.

After owning a number of McIntosh Amps and PreAmps and unpacking them. And if you had original McIntosh packing, I say in all confidence that the glass could not be broken unless (A)there was a hole through both boxes aligning with the point of impact or (B)the boxes showed unmistakable evidence of damage suffered from impact of dropping, crushing or abuse.

If this buyer waited more than 1 hour after opening the box to alert you to the damage, then he had to have done it during unpacking. McIntosh designs their packing to be overly protective to a fault.

What does this guy want you to do? Buy it back? Pay for the repair? Reduce Price?
Has he sent you a picture of the broken glass?

Proceed with caution.

Assuming you insured the item and shipped the Mac to the purchaser then I
believe its your responsibility to make a claim. If the claim is paid, the payment
is sent to you the shipper.
With that said I don't understand why the purchaser waited so long to report
this to you, and I would be suspicious. I'd like to a good answer to why they
waited so long to contact you?
I've purchased and sold a lot of equipment using Audiogon. I've had a total of
two items that I've sold get damaged in shipment, once by FedEx and once by
UPS. I had to jump through all their hoops but I refunded the money to the
purchaser and luckily I receive payment through the insurance that covered my
expense.
In both cases the purchaser had contacted me the day of delivery or the next
day.
BTW; one of the items was cracked glass on a Mac tunner. I was emailed photos
of the damage and we had several discussions on the phone.

Audio Classics can maybe help you out. They have all sorts of Macintosh items to repair and replace. I'm sure they can help you.

http://www.audioclassics.com/brand.php3?brand=McIntosh

Good Luck

Rick