Royce 2-097 Tuner

Looks like you have four settings, SWR, power, modulation, and field strength. With the dial on the power setting, you should just key the mic and read the top line of the meter for power out. The power switch is for 15 watts low, or 150 watts high. For most CB radios you would just leave that switch in the 15 watt position.

With the dial in the FS mode?, you will key the mic, adjust the calibrate knob till the needle reaches the far right of the meter to the word cal. Then you should be able to switch to SWR mode and read the middle line for SWR. Now the problem is, I'm not sure which mode is for calibration setting on the meter. I guess you will just have to experiment and see. It's possible that the power mode maybe used for calibration, but who knows. I'm trying to think how an old radio shack meter like this worked. I remember putting the meter on modulation mode, flip a switch and key the mic and adjust the needle to the cal indicator on the meter, then flip the switch back and talk into the mic and read the percentages on the meter. But I must admit, this meter has me stumped as far as the calibration goes. It seems to be missing an extra switch to take it out of calibration mode.

 

Well you have to put it into the SWR position, the toggle (slide switch) in the middle is for setting the calibration and the SWR testing. The FS seting is for the Field Strength testing which the unit should have a little antenna with it.

The slide switch also is used for modulation, 15 watts on the top and 250 on the bottom. I don't have the instructions avalible, they are packed in the storage container but I think this also is used for the power setting. One of the Royce's tuner/power meter only used the switch just for the power, nothing else while the other used it for the modulation.

The unit was made between 1974 and 1980. It was a base station unit, I remember them being at Royal Radio where I used to buy most of my CB crap from, didn't sell well. I think they went for $34.

 

Okay, so the middle slide switch that says MOD also sets the calibration. That's interesting I never would have guessed that. Although it would make sense versus using a mode switch like I suggested. It's looks like a heavy duty meter, of course they all were back in the 70's thru 80's. As I was part way into my reply, I realized there was a switch pulling double duty in order to calibrate the meter. I just wasn't sure which one. Then it hit me, that was probably why the OP was asking a question about it.

Edit: I just found a picture of the Olsen CB 457 meter, and it does show the words "FWD, REF, and SET on the middle slider switch along with MOD.
I must have missed that on the picture of the Royce 2-097 meter. My mistake.
So Black sheep, to check SWR, flip middle switch up, key mic, adjust calibration knob to CAL on right side of left meter. Then flip switch down and read the middle SWR line on the meter. Sorry for the confusion.