Guess SPI slave from protocol

I am buying chips from eBay and AVRs sometimes come preprogrammed with some code. For fun I download the code and try to understand it (I am strange, I know). The last shipment of ATTiny13A had a simple setup: one mysterious SPI slave and one analog input. It periodicaly reads the input and updates the slave.
The function sending data is simple, the original C was something like:

void sendData(byte register, byte data) {
sendByte((register <<1)|1);

Data are send MSB first, MOSI changes just after the rising edge of clock. The clock is stable for about 1 us, giving probably 500 kHz target clock speed.

After a reset a long sequence of commands is send to the mysterious slave:
Register → Data
0x00 → 0x55
0x02 → 0x03
0x0F → 0x80
0x04 → 0x00
0x03 → 0x10
0x05 → 0x3C
0x06 → 0x20
0x07 → 0x64
0x08 → 0xAA
0x0B → 0x00
0x0C → 0x80
0x0F → 0x00
0x13 → 0x50
0x14 → 0x40
0x15 → 0x20
0x16 → 0x00
0x17 → 0x00
0x18 → 0x00
0x19 → 0x00
0x12 → 0x8D
0x0D → 0x00
0x0E → 0x80
Registers 0x09, 0x0A, 0x10 and 0x11 are not used.

During operation only two registers are written - to the register 0x05 is always written 0x3C and then some number obtained from the ADC result is written to 0x00. (It is “nearly linear” transformation giving result from 0x4D to 0x82 - 77 to 130.)

Does anyone know what this mysterious slave may be? Maybe some wireless link device like nRF24L01?

Why not do an ASCII dump of the code you downloaded and read the text it may be there.

It does not look like ASCII to me.