Possible serial numbers to fill in blanks in C&R Guide

[Profiteer61]

I have 2 SKS 56 that are not 100% numbers matching. Both receivers may fill in some blanks in the "Chinese Type 56 SKS C&R Guide, Triangle Arsenals".
The first is /256\, 1719333(9). The last "9" is a totally different font than the first "9". That's why I put it in parentheses.  I posted this on Gunboards and someone replied that the last "9" was stamped by the importer because there were 2 identical serial numbers.
Whether it's 1,7xx,xxx or 17,xxx,xxx it may fit into the 1972 dotted box.
The second receiver is /136\ 1,712,542 and may also fit into the 1972 dotted box.

[running-man]

Nice carbines both!

The /256\ last nine is most certainly not part of the original serial number.  We only have a single year 17 entry for that Arsenal and it is indeed a seven digit number.

The /136\ is the only year 17 example I have seen.  There are year 16 & 18 so it was assumed they existed but it's none to have an example now!  Very good data, thanks! 

[Profiteer61]

Any idea what this means?

[Greatguns]

Most likely inspection stamps