I have one these, which I picked it up at a local Hamfest, except it's the one without the meter.
The seller said the Levell was beyond repair, but it was in a nice leather case which I could "maybe use for something", so I bought it for $A4.
When I opened it, I found that it used four Eveready 276 9 v batteries.(the ones with the "press stud" connectors).
These were badly corroded, as were the connectors.
That battery package wasn't ever sold in Oz (we had the 276P with the bakelite socket on top), so it looked like my little Levell had been brought here all the way from the UK, & the previous owner had never changed the batteries since.
For shame!
The only 9v batteries available here these days are the small ones we use in DMMs, pocket radios, etc, so I had to buy some battery holders for AA cells, & connect them up.
Well, when I turned it on, the Levell went like a charm, & I was very happy with it, till I had an enforced break from Electronics, (due to a Total Knee Replacement) & when I looked at it next, the AAs had all corroded, killing the holders.
After criticising the previous owner for the same thing, I was pretty much "Hoist with my own petard!"
I'm quite sure, however, that once I fit the new holders & batteries, It will come back as good as new!