Dr. Anya Sharma, a digital archivist at the University of Wessex, is tasked with preserving a collection of historical manuscripts that document the linguistic transition from Old English (Anglo-Saxon) to Middle English. The collection includes a diverse range of texts, from early Anglo-Saxon chronicles to later works exhibiting clear Middle English characteristics. The manuscripts display a spectrum of linguistic features, reflecting the gradual evolution of the English language over several centuries. Anya needs to select the most appropriate ISO 639 code(s) to accurately represent the language(s) of these documents within the digital preservation metadata schema. Considering the nuanced linguistic variations and the need for precise identification of the language stages represented in the collection, which ISO 639 standard and strategy should Anya employ to ensure the long-term accessibility and accurate description of these historical texts? She must also consider that any future researcher should be able to differentiate between the old and middle english texts.