Old English was spoken in what is Great Britain today between the 7th and 11th century. Anglo-Saxons, Jutes, Frisians, and Vikings brought their languages to what is England today and created a hybrid language. This was a slow process over centuries. Of course, there is plenty of evidence of Old English in its written form. The most famous example is the epic poem Beowulf, which is thought to have been written by an unknown Anglo-Saxon poet in the late 10th or the early 11th century. So if you look for old Beowulf manuscripts or anything around that time period, you'll see letters and typefaces usually associated with Old English.
By the 10th century, Alfred the Great had successfully turned this vernacular English into the standard language at the time, which can be found in poetry of that era, e.g. Aelfrich’s 10th Century 'Homily on St. Gregory the Great':
Eft he axode, hu ðære ðeode nama wære þe hi of comon. Him wæs geandwyrd, þæt hi Angle genemnode wæron. þa cwæð he, "Rihtlice hi sind Angle gehatene, for ðan ðe hi engla wlite habbað, and swilcum gedafenað þæt hi on heofonum engla geferan beon.
In this example we can see some words that are identical to today's English:
- he, of, him, for, on.
Other words are very similar:
- 'nama' à name, 'comon' à come, 'wære' à were, 'wæs' à was
And words that have made it into modern English in altered form:
- 'axode' à asked, 'hu' à how, 'rihtlice' à rightly, 'engla' à angels,
'habbað' à have, 'swilcum' à such, 'heofonum' à heaven, 'beon' à be
And words that do not exist in modern English anymore:
- 'ðeode' à people/ nation, 'cwæð' à said/ spoke, 'gehatene' à called/ named,
'eft' à again, 'wlite' à appearance/ beauty, 'geferan' à companions
There are also letters in Old English, such as þ ('thorn') and ð ('edh' or 'eth') that have since been replaced by 'th' in modern English. So as far as letters and typefaces are concerned, you'll also need to watch out for those.