From Apollo 7 forward, each crew of a US manned space mission has brought Robbins medallions with them. The Robbins medallions are a metallic representation of the mission patch. They are normally a little larger than a half dollar. As you might expect, different mission's Robbins medallions are worth different amounts of money. It's both a function of how many Robbins medallions were carried on the flight, and how "sexy"/important the flight was. During the Apollo era the number of flown Robbins silver medallions ranged from 80 for Apollo 17 to 450 for Apollo 11. Even though the number of Apollo 11's medallions is by far the largest (Apollo 13 is the second most common at 404, and Apollo 9 is the third most common at 350), it is also the second or third most expensive of the Apollo Robbins medallions, generally with a price in the $25,000 - $35,000 range depending on quality etc. It is believed that all the flown silver medallions were flown in Earth orbit or Lunar orbit depending on the specific mission. Each of the Apollo crews also brought along a few gold medallions for the crew and their wives. Apollo 7 is the most common with 7 gold medallions. Three missions; Apollo's 8, 9 and 11 only brought 3 gold medallions each, one for each crew member. It is believed that the gold medallions that flew on lunar landing missions all flew in their assorted LMs to the lunar surface. Neil Armstrong's Apollo 11 gold Robbins medallion just went up for auction today, July 16, at Heritage. It just went for $2,055,000. That is over 20 times what the next most expensive Robbins medallion (an Apollo 13 gold one) went for. Clearly only one person was going to win it, and obviously there were multiple people bidding on it. I wonder at what point it winnowed down to 2 people with big checkbooks duking it out. Here's a picture from Heritage of the obverse of the Robbins.