CITIZEN Calculator DM-502 Retro Calculator 10-Digit Solar Calculator Business Calculator

Thank you for viewing.
This is a retro calculator found during decluttering at my parents' home.
I couldn't bring myself to dispose of it because it still works perfectly, so I've decided to list it in hopes that someone can use it.
I would appreciate it if those who like retro items would consider it.

[Main Calculator Functions]
Power: Designed with a combination of a solar panel and an internal battery.
The internal battery has not been touched. It operates solely on the solar panel, and the display is clear.

10-Digit Display: With more digits than a typical 8-digit calculator, it can handle calculations in the hundreds of millions, practical business use, and bookkeeping practice.

Keys: Equipped with keys such as M+ (Memory Plus), M- (Memory Minus), and MR (Memory Recall), allowing for complex combinations of the four basic arithmetic operations.

[Common Calculation Function Test for All Manufacturers]
The following items have been self-checked.

① For calculators that do not support hidden commands, you can perform a simple check for missing dots or malfunctions in the calculation functions by performing the calculation covering all keys below.
1. Enter 12345679 (omit the 8).
2. Press × 9 ＝.
3. If the LCD displays 111111111, with all 1s lined up, then the main digits, multiplication, and equals keys are normal.
4. Continue by pressing × 2 ＝ to get 222222222. By changing the numbers, you can check the lighting of each LCD segment.

② Special Key Confirmation
Check if settings are correctly reflected by operating parts other than numbers and basic arithmetic.
* Decimal Point Selector (F, 3, 2, 1, 0, ADD2)
    * Set the switch to 2 and calculate 1 ÷ 3 ＝. If the screen shows 0.33, it is normal.
* Rounding Selector (Truncate, Round to Nearest, Round Up)
    * Set to Round to Nearest (5/4), and after calculating 1 ÷ 3 ＝ (0.33...), check if the rounding is performed correctly to the correct number of digits when adding 0.01, etc.
* Independent Memory (M+ / M- / MR / MC)
    * Press 5 M+, and confirm that the M mark lights up on the screen. Then, press MR to recall 5, and if the M mark disappears when pressing MC, it is normal.

③ Solar Panel Sensitivity: Check if the LCD becomes faint or disappears when the solar panel is completely covered by your finger.

④ Key Feel: Press all buttons to check for any sticking or double input (chattering) from a single press.