Another quick rating system

A few years back I posted about a Quick and Dirty Rating System. While going through back issues of the CCLA Record (the forerunner to Australian Correspondence Chess Quarterly) I found a similar but even more basic system.
Calculations are on a game by game basis and works as follows. Firstly you find the difference between the 2 players ratings, rounded up to the nearest 20 points (RD). The if the higher rated player wins they gain 50-RD/10 points while the loser loses the same amount. If the lower rated player wins the gain is 50+RD/10 points while again the loser drops the same number of points. In the case of draws the lower rated player gains RD/10 and the higher rated player loses the same amount. The rating differences are capped at 500 points so the biggest rating increase possible is 100 points per game.
Again this system isn't as accurate as systems built on stronger mathematical models, but for a local chess club it is easy to implement, understand and use.