Just a bit more on the meter.
Looks very interesting; I've never seen one like this with 20,000 ohm per volt and no selector switch.
Firstly, I guess the meter has 2 battery sets; one set is a single or double 1.5 volt , and the other is a 9 volt. You might like to check this.
To measure ohms (or continuity), or the infra red diode, connect one test lead to the ohms connector at the bottom LHS. The other lead goes to ohm x 1. When you short the test leads together, the meter will move to the right side of the meter scale. Set it on 0 ohms by adjusting the 'reg' control. the top scale will read ohms. One of the test leads will be negative with respect to the other. For testing a diode, the negative lead connects to the cathode of the diode. This is, I believe, the black lead on term #706. Anyway, one way you get conduction, the other way you get no conduction. It is possible that the ohm-meter, by its design, doesnt have sufficient internal voltage from the battery to get any conduction in the diode. So, if you use the ohm x 10,000, you should be able to get conduction. To use ohm x 10,000 transfer the test lead from the bottom LHS to the V pf ohm x 10,000 terminal, and transfer the top lead from ohms x 1 to the Hz, pF x 1 ohms x 10,000 terminal. Check the LED unit again. If you get conduction this time, the needle will swing pretty much all the way over to the RHS.
Note on the ohm scale, that 50 (45?) ohms is at the centre of the scale. Assuming the voltage source for the ohmmeter function is 3 volt, the the full scale current when setting the ohm reading with 'reg', will be 60 milliamp. For checking diodes in general, such a high current may damage a diode such as a red or green led. For checking such diodes, use the ohm x 10 scale, by moving one test lead from the ohm x 1, to the ohm x 10 terminal. This will place a 500 ohm resistor in the ohms circuit and the test current will be only 6 milliamp.
The 'LOW ohm connection terminals are interesting too. It is conceivable that there is a 5 ohm resistor as part of the current shunt which is used for the low ohms range. This would be effectively a 'ohms divided by 10' scale.
The good old analog meter is VERY useful for measuring the conduction characteristics of diodes generally. To do this needs a linear voltage scale starting with zero at the full scale position (just like the ohms range) and the ohm-meter battery voltage at the rest position of the pointer needle. Connect a diode to the test leads, and if say the meter needle stops at half scale, you can say the the diode forward voltage is 1.5 volt (half the battery voltage) and the diode current is 30 mAmp (half the full scale ohms test current). Then change the ohm range to ohms x 10, and check the forward voltage and current. This type of test will tell you about the conduction characteristics of the diode you are examining.