Afghanistan, Barakzaï /Wali Muhammad rupee of Kabul mint (ry 4 ?)

[saro]

This is a rupee attributed to Wali Muhammad who was the ruler at Kabul in 1297 AH / weight: 9,21 g with a black patina.
There is no ruler's name but :
- obverse : "ya sahib al-zaman" (Ô Lord of the Time)
- reverse : " zarb dar al-sultanah Kabul"
The AH date is off on this coin but is present on this type on both faces and allows its attribution to this ruler :
cf Zeno:  http://www.zeno.ru/showphoto.php?photo=87183

Two details on this rupee haven't been noticed or discussed :
- it is dated 1297 AH, which is the only year of reign of Wali Muhammad but what could mean the digit "4" associated on reverse 
- what means the letter "S" in center of obverse ? ( may be "S" for "Sardar", a tittle of Wali Muhammad ?)

If somebody knows....

[@josephjk]

Or 'S' for Sahib maybe..?

There is a similar coin here..... KM538

[saro]

Thousand thanks for these pictures with description; I am pleased to see that I am not the 1st to be surprised by this digit 4 !
May be the "S" is for "Sahib" ? even if "sahib" is already written in full word on the coin.
The KM 538 dated 1297 doesn't shows S & 4, this one could be a variety ? not sure it is very scarce..