Answer: the top signature is authentic.
Bonus: The less authentic signature was created by William Henry Ireland, who forged documents by Elizabeth I, Shakespeare, and others in the 1790s.
SPP: The Shakespeare scholars and editors, George Steevens and Edmond Malone, had this and other signatures copied from the original documents, as the basis of the copperplate engravings for the plates illustrating their 1778 edition of Shakespeare’s plays. William Henry Ireland used these images as the basis for many of his forgeries.
The authentic and forged signatures were gathered in the volume shown here by William Henry Ireland, who reproduced his “original” authentic forgeries of Elizabeth and Shakespeare to sell to collectors, long after the forgery itself had been exposed in 1796 by Edmond Malone and others. William Henry Ireland, The Shakespearian [sic] Productions. England, 1805. Osborn fd83]