Original receipt for slave sawyers' extra wages

The National Archives and the U.S. Capitol Historical Society have put photographs of work records relating to the hired slaves on-line. Thanks to the photocopies I took in the Archives in 1989-90, I have scanned far more records, but those institutions certainly do a better job. (I tried to get down to the Archives to photograph records while writing Slave Labor in the Capitol but the Archives claimed they didn't know where the records are!) The trouble with my photocopies is that to save money I tried to copy two payrolls at a time and I made notes on the photocopies. The images below, provided by the USCH, show the true current state of the records.

I have this image in another post http://capitalslaves.blogspot.com/2015/03/payrolls-showing-extra-wages-for-slave.html

but after posting that I've been going through my records again and noticed that there is a folder for the document that clearly labels the pay as "Extra wages." It also shows that the money was paid out on September 5, 1795, just 6 days after the payroll was signed by the foreman of the carpentry work at the Capitol. In general hired laborers or their masters were only paid every quarter, every three months. September 30 would be their payday for work done since June. The slave sawyers were treated just as skilled workers were, paid every month.

In my book I was careful not to exaggerate the contributions of slaves just I was careful not to exaggerate the talents of white skilled workers. The slave laborers paid extra wages to do sawing are the heroes of my book. That said, I don't think it right to call them skilled workers. That label belongs to the traditional building trades, but I don't think we should downplay the fact that slave sawyers were paid after a month's work like skilled laborers.

Examining the payroll below, probably for the hundredth time, I think I learned something new. In most of the payrolls for sawyers, the mark "x" at the end of the line listing their days worked and rate of pay (always 1 shilling), all look the same. In the payroll below it is noted that the receipt of money was "witness our hands" but there are not the usual x's. I just realized that the marks in front of the name might be how the slaves witnessed the receipt of their wages. Are their marks an attempt to write the first letter of their name? If so, it's the only example I've seen. Payrolls with illiterate free laborers or slaves getting extra wages used the traditional legal formula of "X his mark." Unfortunately the right side of the document is damaged but I don't think there is enough room for the usual "X his mark."