Apple macbook charger 85W Magsafe 2 - MD506HN/A vs A1424

I have a late 2013 15 inch macbook pro. The model number on the charger is A1424.

Even on apples website this model number is not mentioned in the 85W charger listing. It shows up as

MD506HN/A.

Authorised online sellers also list the only 85W charger available for magsafe 2 as MD506HN/A. I am unable to buy directly from Apple as they probably don't have it in stock and are claiming 6 weeks for delivery (Indian Apple website).

What is the difference between A1424 and MD506HN/A. My macbook pro is purchased in Australia and I am now in India - is this just a country specific difference in the model number?

I have looked at the charger compatibility page on Apple and it only states wattage and connector and not exact model number.

1. Could I know the difference if any between the MD506HN/A and A1424?

2. How do I find out why there is such a long delivery time for the charger in India? I don't mind the wait as long as the original apple product lands up in a month or so. I don't want to finally get a note saying it's not available and end up with a cancelled order.