This guide will assume you are playing on a mostly vanilla server that doesn't alter the game so that coins would be able to be acquired or destroyed in other ways, and it will have content that is mostly found on the official SCP: Secret Laboratory wiki page available here[en.scpslgame.com]. If the server you are playing on does utilize coins in a special manner then of course you could account for that. However I did find out that the wiki is missing some crucial information on how to acquire coins, so let's begin

The wiki page[en.scpslgame.com] about coins doesn't detail where they can be found but they are mostly documented on other articles under Site-02[en.scpslgame.com] like the Weapon Locker Type 21, Standard Locker, and some rooms in HCZ. Coins can also be acquired through SCP-914.

• The Standard Locker has a 5% chance of spawning between 1-4 coins inside one of its chambers.
  

  

• The Weapon Locker Type 21 has a 11.1% chance of spawning between 1-30 coins inside its drawer at the bottom which does not require any keycard.
  

  

• SCP-106's Containment Area has a guaranteed spawn for a single coin on the leftmost shelf.
  

  

• SCP-079's side-room with the re-containment button has a guaranteed spawn for two coins on top of the MTF-E11-SR rack located above the three heavy armour spawns. This location is to my knowledge undocumented as the wiki page[en.scpslgame.com] does not say anything about it at the time of writing this guide.
  

  

Coins can only be acquired in one way through SCP-914 and that is by inputting heavy armour on the fine or very fine setting. This will transform it into a singular coin. Armour exists inside its own sort of cycle; armour cannot be duplicated and another item cannot be transformed into armour. Inputting a coin on any setting but rough will just result in a coin. Inputting a coin on rough will destroy the coin.

This section will elaborate on the total value of your hard work. The coin in SCP: Secret Laboratory is a Quarter Dollar so they will amount to 25 cents each. Here's a quick run down again on everything you can find naturally:

• 1 guaranteed coin in Larry's chamber
  
• 2 guaranteed coins in Computer's containment
  
• 1-4 potential coins in every locker
  
• 1-30 potential coins in the weapon locker drawer

Possible spawn locations for the lockers are: 1 in GR-18, 1 in PT, 1 in PC-15, 1 in VT, 2 in the walkway office, and 1 in the cubical office. This amounts to 7 possible lockers at most and also at most 7 * 4 = 24 total coins from the lockers alone. Take these together with the guaranteed weapon locker that may hold coins and the 3 naturally spawning coins and you have a potential of 24 + 30 + 1 + 2 = 58 total coins without using SCP-914. Now also take into account that there can spawn:

• 1 potential armour piece in LCZ 012
  
• 4 potential armour pieces in the weapon locker
  
• 3 guaranteed armour pieces in computer's room
  
• 3 guaranteed armour pieces in the LCZ armoury

Which would mean a potential of 58 + 1 + 4 + 3 + 3 = 69 total coins (nice). This doesn't consider the fact that other people may spawn with armour pieces (such as Chaos or MTF personnel) so if you happen to run into any Facility Guards or something on the way you could convert them into coins. Of course, you're on a time limit because LCZ will decontaminate at some point so it's probably going to be pretty tough to get all of this together.

Anyhow, 69 coins = 17.25 USD = 14.87 EUR = 12.57 GBP which is probably much more than you would ever get paid otherwise as a D-Class, you might just be able to pay off your mortgage