That seems to make sense with what I just found JM. I just came across this from the "LIST OF MEMBERS OF THE CLOCKMAKERS' COMPANY OF LONDON, FROM THE PERIOD OF THEIR INCORPORATION IN 1631 TO THE YEAR 1732.1 By C. OCTAVIUS S. MORGAN, F.R.S., F.S.A." and, if I'm reading this correctly, it shows John Long admitted as a "Brother" in 1677 (highlighted below) as designated by the lower case "b" accompanying his name for that year and again in 1698 which could be the year of his incorporation although I cannot explain the 21 year gap.
THE CLOCKMAKERS COMPANY.
Page 207
1682 Knight, Richard 1684 c
Kenning, William b
1685 Knight, Charles 1686 Kenton, Joseph 1688 Kemp, Charles 1689 King, Jonathan 1701 Kinning, John Kemp, Richard 1712 Kissor, Samuel Kanns, John 1715 King, John 1717 Keddon, Daniel 1719 Kendrick, John 1720 King, William King, Henry 1722 Kirby, Robert 1723 Knight, Henry Kelton, Simon 1726 Kendrick, John 1729 King, John'L.oh.
1631 a Lynaker', Samuel,
one of
the
first Assistants)
ante "16501632
a Lambe, Thomasa Lord, Richard 1641 Le Grand, James
b Louarth, Jasper b 1642 Laxton, Thomas b
1647 Le Grand, Francis b
1648 Light, John b
1649 Loomes, Thomas 6152 Langford, Goring b
1653 Laxton, Thomas La-well, Paul b
. Layton, John b
Long, Thomas 1655 Lochard, John 1656 Lello, James b .
1663 Lucie, John 1664 Langley, Thomas Legrand, James, junr. 1668 Lloyd, William 1669 a Lucas, William 1670 Lynch, Robert Lloyd, William 1672 Longford, Ellis 1673 Lloyd, Joseph 1674 Lake, Bryan 1675
aLambe, Edmund 1676 Lee, Cuthberta Leconte, Daniel b
1677 c Longland, John
b Long, John
b Lloyd, David 1680 a Lounde, Jonathan 1681 Lloyd, Richard 1682 a Loundes, Isaac
b 1683 a Laughton, William
b 1685 Leake, Eaith1687 a Le Comte, James bc
Le Feburg, Charles (French)1689 Lodowick, Peter 1691 Lloyd, Charles 1693 Leake, George 1694 Lumpkin, Thomas Lee, Samuel 1697 a L'Estrange, David b
a Lester, Thomas b
1698 a Littlemore, Whitestone (ap.Tompion)Long, John 1700 Lloyd, James Latham, John 1701 Lushbrook 1702 Lovett, William 1703 Lyne, William 1705 Lewis, John 1706 Langley, Cornelius Ludlow, Samuel Leroux, Alexander 1709 Ladd, Ladd 1711 Lens, William Ley, William 1712 Limoniere, Stephen h 1713 «Lamp, John 1715 Lashbrook, Henry 1718 Langcroft, Richard 1719 Lee, John 1720 Lany, John Leffin, Thomas Luttman, William 1721 Le Sturgeon, David 1722 Lloyd, James 1724 Legg, John 1725 Lewis, Ambrose 1726 Layton, Francis 1727 Lucas, Edward 1730 Leigh, Thomas Latour, Rene 1731 Lucas, Henry Lewin, William