Hanafi
The sources give no view for it here.
البيع على الرقم
هل يجوز البيع على الرقم المكتوب على السلعة؟
Each school’s answer
In our wordsHanafi
Not stated in the sources
Maliki
Not stated in the sources
Shafi'i
Not stated in the sources
Hanbali
Not stated in the sources
The texts
١٥١٧ - مَسْأَلَةٌ: وَلَا يَجُوزُ الْبَيْعُ عَلَى الرَّقْمِ وَلَا أَنْ يُغْرِ أَحَدًا بِمَا يُرَقِّمُ عَلَى سِلْعَتِهِ، لَكِنْ يُسَوِّمُ وَيُبَيِّنُ الزِّيَادَةَ الَّتِي يَطْلُبُ عَلَى قِيمَةِ مَا يَبِيعُ، وَيَقُولُ: إنْ طَابَتْ نَفْسُك بِهَذَا، وَإِلَّا فَدَعْ. [مَسْأَلَة البيعتان فِي بيعة]
From the schools’ own books
Maliki
The sources give no view for it here.
Shafi'i
The sources give no view for it here.
Hanbali
The sources give no view for it here.
What is «in our words» is our standard wording; the books’ texts stay as they are.