The manual doesn't mention anything about awarding medals and honor except for the Crux Terminatus and since I love this kind of dettails about a character I made this little thing up based on Codex info. I divided the medals and honors in 3 tiers, each giving reknown accordinly.
Honors for astartes are not just medal objects in a box near the been, their honors are carven into the armors and weapons they use, any other Astartes looking at another brother can recognize immidiatly what he has been awarded with just by looking at his armor.
The Marksman Honour 1
Imperialis 1
Purity Seal 1
Aquila 1
Skull and Motto 1
Iron Skull 2
Imperial Laurel 2
Valor Crest 2
Vicotrex Alpha 2
Iron Halo 3
Terminator Honor 3
Honorifica Valorum 3
T1 Can be awarded multiple times (or at least it seems by the awards on some minis)
T2 and 3 can be awarded only once AFAIK