What # of master lock is this. ?

[jimmysmith]

a buddy and I were going through some boxes left in a house he bought, boxes completely full of junk,,,he pulled out this lock...so of course I snached it out of his hand and said MINE! tossed it in my bag and later on when I got back to my place I pulled it out and started to check it out..
it has no key... picked it in a matter of about 50 sec. bumped it in about 20 sec. after a healthy shot of wd-40. Its has a m1 key way..4 pin's. i plan to impression it {so Ill have a key}. What my question is ... around what year could it be.. ? when was it made? what # is it if any? I can see on the top of the front side it says 77... now could that be the # ? my father said it could be the #, but he thinks its more like a locker number..like maybe its only one of many that was on a set of lockers. I dont know myself.. thats why I am turning to you guys. Does anyone know anything about these locks?
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[Shrub]

Sorry but i had to turn your pics to links as they were really big,

[Cybernation]

I would have to say 77 since that is the only number on there but then again it looks to be to old for it to have any of the numbering schemes used today.

[JackNco]

VERY old, looks cool though. first of stop killing ur lock with WD40. nice one to add to the collection though

[jimmysmith]

I was left with no choice, the pins were so stuck it was not funny. wd-40 did the trick....always works well for me..

why would it be a bad idea to put wd-40 in a lock?

[Jow]

liquid or wet lubricants although initially freeing up the lock, will attract dirt and the dirt and grime will stick to the lube. This is not the case with dry lubricants.

[lunchb0x]

if you want to clean it out properly soak it in shelite to clean it out, then you can use graphite in it

[jimmysmith]

I see, I will remember that, I have been using wd-40 on locks for years, ... mainly just to free them up a little just for opening, appreciate your advice.